What if, Grumman went with a fixed wing for the Tomcat

[Manuducati]

I give up debating with you on the subject as you keep repeating the same things without taking into consideration what multiple contributors are trying to explain.
Have a nice day.

 

[Mirage4000]

I give up debating with you on the subject as you keep repeating the same things without taking into consideration what multiple contributors are trying to explain.
Have a nice day.

View attachment 658195

Try to be honest see theses sources

The last flight of the F-14 Tomcat in US service took place October 4, 2006, with the final flight retirement ceremony on September 21, 2006. Two F-14’s were readied for the ceremonial final flight; after the primary plane experiencing mechanical problems, a backup was flown instead. The failure was a reminder of one of the reasons for the retirement, high maintenance costs. The F-14 Tomcat was officially retired on September 22, 2006 at Naval Air Station Oceana. The F-14 fleet is mothballed at the Davis-Monthan “Boneyard.”

Grumman F-14D Tomcat – Prairie

The initial acquisiton cost of an F-14 is quoted by the US Navy at around $38 million. However, the primary disadvantage of the aircraft is not its purchase cost but maintenance expenses. As discussed previously, the life-cycle costs of operating and maintaining an aircraft far exceed the initial acquisition cost. These costs only grow as planes age and require increasingly more maintenance hours per flight hour. This trend has hit the F-14 harder than most of its contemporaries because of its complex airframe (including the variable-geometry wings) and harsh salt-air environment at sea. The F-14 is currently the most expensive aircraft to operate in the Navy inventory, requiring 40 to 60 maintenance manhours per flight hour. For comparison, the F-18 Hornet requires only 20 hours of maintenance and the latest F-18E/F Super Hornet requires just 10 to 15 hours. These high maintenance costs played a large role in the Navy's decision to move the retirement of the F-14 up from 2010 to 2006.

Aerospaceweb.org | Ask Us - F-14 History and Performance

​

Maintenance Upgrades​

One of the most common justifications for a new design aircraft is that the existing one is too maintenance intensive (even though it was undoubtedly considered a vast maintenance improvement over its predecessor!). Consider the F-14 Tomcat and its replacement, the F-18 Hornet. No one had any real performance issues with the F-14 Tomcat but it was considered to be too maintenance intensive.

Maintenance Upgrades

One of the most common justifications for a new design aircraft is that the existing one is too maintenance intensive (even though it was u...

navy-matters.blogspot.com

The decision to incorporate the Super Hornet and decommission the F-14 was mainly due to high amount of maintenance required to keep the Tomcat operational. On average, an F-14 required nearly 50 maintenance hours for every flight hour, while the Super Hornet requires five to 10 maintenance hours for every flight hour.

This Was the Last Time the U.S. Navy's F-14 Tomcat Went to War

A sad story?

nationalinterest.org

The question is you do not want to see the variable geometry wing was one of the main reason it had a very high need for maintainace and that killed the further production and deployment of F-14 besides it was too expensive

 

[aim9xray]

Can you provide any substantive evidence that the F-14's variable geometry wing had a very high need for maintenance? Any source documentation? Do you know what the top 10 maintenance drivers were?

Protip: source documentation (not endlessly repeated web comments) will build your case.

 

[Archibald]

I think it was in an old thread in that forum about "evolved Tomcats" from the D to the ASF, Tomcat 21, @F-14D explained one of the few advantage of the Hornet and Superbug over legacy Tomcat related to hydraulics and wiring - that was the main maintenance weakness of older F-14.

In the early 90's when both Superbug and advanced Tomcats were considered it was found that correcting the wiring and hydraulic maintenance-intensive aspects of the Tomcat would amount to a deep internal rework of it, making it much more expensive.

The boundaries between the two was (more or less) F-14D (old maintenance intensive systems, but already in service) versus Tomcat 21 / ASF something (1990's tech level instead of late 60's: big difference)

Hornets & Superbugs, for all their flaws elsewhere, were and are a generation ahead of the Tomcat here. Don't forget that through the F-111B the Tomcat related to the F-111, pre-1964 tech levels. The Hornet had a decade of advanced tech or more (1978 and beyond).

As far as flight controls are concerned, the Tomcat was manual control / hydraulics when the Hornet was computer / digital: two generations ahead, the intermediate step being the F-16 analog controls.

I'll try to find the thread and relevant posts...

SHAZAM

https://www.secretprojects.co.uk/threads/f-14-tomcat-projects.589/#post-46933

Tons of excellent stuff there. Particularly this post, for a start.

https://www.secretprojects.co.uk/threads/f-14-tomcat-projects.589/#post-21613

 

[SSgtC]

I think it was in an old thread in that forum about "evolved Tomcats" from the D to the ASF21, @F-14D explained one of the few advantage of the Hornet and Superbug over legacy Tomcat related to hydraulics and wiring - that was the main maintenance weakness of older F-14.

In the early 90's when both Superbug and advanced Tomcats were considered it was found that correcting the wiring and hydraulic maintenance-intensive aspects of the Tomcat would amount to a deep internal rework of it, making it much more expensive.

The boundaries between the two was (more or less) F-14D (old maintenance intensive systems, but already in service) versus Tomcat 21 / ASF something (1990's tech level instead of late 60's: big difference)

Hornets & Superbugs, for all their flaws elsewhere, were and are a generation ahead of the Tomcat here. Don't forget that through the F-111B the Tomcat related to the F-111, pre-1964 tech levels. The Hornet had a decade of advanced tech or more (1978 and beyond).

I'll try to find the thread and relevant posts...

I think I remember that thread. IIRC, the "D" model already had greatly reduced maintenance requirements compared to the "A" model. And the ST21 would be lower still. Mainly down to the total replacement of all remaining analog systems with digital ones and the reduction of wiring in the airframe (along with replacement of a number of screwed on access panels with hinged easy access panels).

 

[Archibald]

Yeah you nailed it very well.

 

[Mirage4000]

Can you provide any substantive evidence that the F-14's variable geometry wing had a very high need for maintenance? Any source documentation? Do you know what the top 10 maintenance drivers were?

Protip: source documentation (not endlessly repeated web comments) will build your case.

The last flight of the F-14 Tomcat in US service took place October 4, 2006, with the final flight retirement ceremony on September 21, 2006. Two F-14’s were readied for the ceremonial final flight; after the primary plane experiencing mechanical problems, a backup was flown instead. The failure was a reminder of one of the reasons for the retirement, high maintenance costs. The F-14 Tomcat was officially retired on September 22, 2006 at Naval Air Station Oceana. The F-14 fleet is mothballed at the Davis-Monthan “Boneyard.”

Grumman F-14D Tomcat – Prairie Aviation Museum
this is a museum of aviation thus you can consider it a good source.

Now this is an official source consider here they say money matters early in the F-14 program Grumman was delivering an overpriced jet and not achieving the goals upon the budget they promised here are some extracts


A valid schedule variance could be determined by comparing the planned value of work scheduled versus the planned value of work accomplished (PVWA). Likewise, a valid cost variance could be determined by comparing the planned value of work accomplished with the actual cost incurred to complete this same accomplished work. For example, assume that the contractor scheduled $50 worth of planned work but only accomplished $30 worth of this planned work at an actual cost of $100. In this case, an unfavorable cost variance of $70 (actual costs - PVWA) and an unfavorable schedule variance of $20 (PVWS - PVWA) would result. However, in the CASSR this condition would be reflected as an unfavorable current variance of only $50 (actual costs - PVWS). Further distortion would arise if PVWS and actual costs were the same. For example, if PVWS is $100, PVWA is $30, and the'actual cost for this work is $100, then the current variance as reported in the CASSR would be zero (PVVWS - actual costs), while there should be both a $70 unfavorable cost variance (actual costs - PVWA) and a $70 unfavorable schedule variance (PVWS - PVWA). We therefore believe that the current variances as cited in the Cost Account and Summary Status Report are not meaningful.

The estimated cost progression of the program is as follows: Date Quantity Estimate Unit Cost Jan. 13, 1969* 469 $6, 166 million $13.1 million June 30, 1969 469 $6,373 million $13.6 million June 30, 1970 722 $8,279 million $11.5 million June 30, 1971 313 $5,212 million $16.6 million

https://www.gao.gov/assets/092339.pdf

See that originally they were going to purchase 469 aircraft at a price of 13.1 million dollars but by 1971 it went down to 313 aircraft at a price of 16.6 million dollars.

this of course inpacted the F-14B since they say
Most of the total net cost reduction is due to the change in quantity planned for production. The increases in estimated costs were primarily attributed to inflation, the crash of the first aircraft, and development problems on the advanced technology engine. The unit cost has risen primarily due to the development cost being appropriated over fewer aircraft.

https://www.gao.gov/assets/092339.pdf

 

[SSgtC]

The last flight of the F-14 Tomcat in US service took place October 4, 2006, with the final flight retirement ceremony on September 21, 2006. Two F-14’s were readied for the ceremonial final flight; after the primary plane experiencing mechanical problems, a backup was flown instead. The failure was a reminder of one of the reasons for the retirement, high maintenance costs. The F-14 Tomcat was officially retired on September 22, 2006 at Naval Air Station Oceana. The F-14 fleet is mothballed at the Davis-Monthan “Boneyard.”

Grumman F-14D Tomcat – Prairie Aviation Museum
this is a museum of aviation thus you can consider it a good source.

So, in other words, no, no you can't provide any actual evidence. You're using an anecdote from the type's final fight, one that doesn't even specify what the problem was, to try and prove the VG wing is what killed it. Everyone here has acknowledged that the F-14A was a maintenance pig. But as has been pointed out, repeatedly I might add, the F-14D required vastly fewer maintenance hours per flight hour than the "A" did.

 

[Mirage4000]

The last flight of the F-14 Tomcat in US service took place October 4, 2006, with the final flight retirement ceremony on September 21, 2006. Two F-14’s were readied for the ceremonial final flight; after the primary plane experiencing mechanical problems, a backup was flown instead. The failure was a reminder of one of the reasons for the retirement, high maintenance costs. The F-14 Tomcat was officially retired on September 22, 2006 at Naval Air Station Oceana. The F-14 fleet is mothballed at the Davis-Monthan “Boneyard.”

Grumman F-14D Tomcat – Prairie Aviation Museum
this is a museum of aviation thus you can consider it a good source.

So, in other words, no, no you can't provide any actual evidence. You're using an anecdote from the type's final fight, one that doesn't even specify what the problem was, to try and prove the VG wing is what killed it. Everyone here has acknowledged that the F-14A was a maintenance pig. But as has been pointed out, repeatedly I might add, the F-14D required vastly fewer maintenance hours per flight hour than the "A" did.

more maintainence means more money too, less reliability and less flying hours considering F-14 was more expensive than F-18C and less reliable why you will buy more F-14? a museum of aviation has aircraft technicians you will not satisfy because you do not want even believe an aviation museum run by aircraft technicians

 

[kaiserd]

But decisions around what the F-14 would be (including the combination of requirements that led to the adoption of the swing wing configuration) long predate the existence of the F-18.
The F-14 just couldn’t incorporate technology, materials, weapons etc. not available at its time and which came in a generation or more after it.
The swing wing did fall out of use for a reason and undoubtedly impacted the complexity and maintenance costs etc. of the F-14. But a fixed wing alternative Tomcat probably still has nearly all the real F-14s actual issues (and boy it had some issues) while growing some more specific to itself.

 

[SSgtC]

why you will buy more F-14

Because it's a vastly more capable aircraft and could do things that even the Super Hornet still struggles to do. But that doesn't seem to matter to you

 

[Mirage4000]

why you will buy more F-14

Because it's a vastly more capable aircraft and could do things that even the Super Hornet still struggles to do. But that doesn't seem to matter to you

No it is not like that.

If you want to really see why Grumman chose the Variable wing over the fixed wing see this study

To identify the basic effects of variable sweep wings the study included the definition of a parallel design with a fixed sweepback design. This was designed to the same performance specification, using the same design tools and assuming comparable technology levels. This approach eliminates possible systematic errors in the weight and drag prediction methodology to a large extent. The wing comes out much larger due to the lower CLmax, which also drives the empennage area.

http://icas.org/ICAS_ARCHIVE/ICAS2010/PAPERS/071.PDF

This is because the lower aspect ratio and higher sweep angle of the fixed wing increases the size of the wing to achieve the same field performance

. This results in the following comparison (fig 6), when both designs are sized for the same mission performance and the same field performance:

http://icas.org/ICAS_ARCHIVE/ICAS2010/PAPERS/071.PDF

The only reason the fixed wing was inferior was landing performance

The example was the F-15 versus F-14 landing performance, in dogfights the F-15 has an ideal wing but for landing it was inferior to F-14


F-14 also pays in structural weight

Note that the weight penalty of the hinge plus drive system is comparable to the weight saved in reserve fuel alone;

http://icas.org/ICAS_ARCHIVE/ICAS2010/PAPERS/071.PDF

here they are comparing two jets which one has a very swept fixed wing to achieve same performance with one with Variable geometry wing.

On the F-15, the wing is not as swept as the 68 degrees of F-14, but only 45 degrees.

So F-15 is always flying with the angle of sweep F-14 uses at dogfights.

The payment for F-14 swing wing is higher maintenance, and price.

Performance wise the F-14 was good, maintenance wise was it was not, add the extra price well that doomed Grumman that was asking more and more money to fix the aircraft short comings.

I like the F-14 but you really have to see its short comings, it was good but it was expensive to operate and purchase.


This paper presents a broad survey of the structural problems associated with variable geometry for aircraft. Variable sweep allows an aircraft to fly throughout a broad regime of speed and altitude efficiently and without excessive power requirements. Tailored lift drag, improved ride quality, lessening of fatigue damage, and reasonable control sensitivities are advantages. Structural problems fall into two general categories: (1) Because of the number of wing positions, the equivalent of many fixed‐wing aircraft must be investigated, analysed and tested; (2) there are unusual problems which have heretofore not been important considerations in design. Category (1) presents the problem of managing and assimilating large amounts of data. Computer pogrammes and a family of cross‐plots assist greatly. Category (2) presents new fail‐safe criteria, a large lumber of possible flutter‐critical configurations, unavoidable free play in mechanisms which affect flutter speeds, dynamic loads, pivot mechanism bearing life, and requires high reliability in materials. Analyses and wind‐tunnel tests have shown that free play in mechanical joints may or may not cause significant service problems depending upon the mechanical arrangement selected and the actual degree of free play under service conditions.

Structural Problems Associated with Variable Geometry: A review of the problems involved in the structure of variable sweep wings | Emerald Insight

Structural Problems Associated with Variable Geometry: A review of the problems involved in the structure of variable sweep wings - Author: Marvin M. Alexander

www.emerald.com

fly by wire technology and LEX gave way to cheaper aircraft to operate and more reliable, meaning more hours of flight.

F-18E certainly can not do everything F-14 did, but it was more reliable, that counts a lot, plus the US navy never achieved kills with AIM-54.

 

[Mirage4000]

Can you provide any substantive evidence that the F-14's variable geometry wing had a very high need for maintenance? Any source documentation? Do you know what the top 10 maintenance drivers were?

Protip: source documentation (not endlessly repeated web comments) will build your case.

F-14 entered service in 1974 and its wing sweep angle could vary between 20 and 68, as shown in Figure 6, to give the optimum lift-to-drag ratio in flight by automatic control. Sometimes the wings even can be ‘overswept’ to 75 by overlapping the tail to save space. The F-14 is capable of flying and landing safely with the wings swept asymmetrically in emergencies (Wikipedia document 03). More than a half dozen major military aircraft appeared with variable sweep wings during the 1960s and 1970s. However, the large metal gearbox that moved the wings was so complicated and heavy that the maintenance requirements were increased and fuel performance was decreased. By the 1980s, no new work on variable sweep technology has been incorporated into any new production military aircraft in at least the last 15 years (Century-of-flight document).

https://www.tandfonline.com/doi/pdf/10.1080/19373261003607972

 

[aim9xray]

this is a museum of aviation thus you can consider it a good source.

I worked on the F-14 program for about 18 years in an engineering capacity. I had full flightline access in the course of my duties and dealt with the maintainers and officers. I attended and participated in many contractor/customer engineering management meetings dealing with F-14 software, structures and fatigue life.

By your logic (above), you can consider me a good source.

 

[helmutkohl]

this is a museum of aviation thus you can consider it a good source.

I worked on the F-14 program for about 18 years in an engineering capacity. I had full flightline access in the course of my duties and dealt with the maintainers and officers. I attended and participated in many contractor/customer engineering management meetings dealing with F-14 software, structures and fatigue life.

By your logic (above), you can consider me a good source.

in hindsight, knowing what we do now after years of experience and knowledge
how would you have re-designed the F-14 back then if you could have the chance. what would you change if anything?

 

[Mirage4000]

this is a museum of aviation thus you can consider it a good source.

I worked on the F-14 program for about 18 years in an engineering capacity. I had full flightline access in the course of my duties and dealt with the maintainers and officers. I attended and participated in many contractor/customer engineering management meetings dealing with F-14 software, structures and fatigue life.

By your logic (above), you can consider me a good source.

an anonymous source can not be a reliable source, regardless where you worked, more people worked in the program, and more papers give a clearer view, the document i gave you is based upon scientific research give me proof of your identity and your documents published by a scientific and industrial well stablished intitution to back you up, at this moment you have no way to proof you credentials.

Even If you worked, you need to present offical papers that atest your veracity, the documentation by a museum and an aerodynamic study are enough to support a view.

REVIEW PAPER Aircraft morphing wing concepts with radical geometry change Zheng Min*, Vu Khac Kien and Liew J.Y. Richard Department of Civil Engineering, National University of Singapore, Kent Ridge, Singapore 119260, Singapore (Received 26 December 2008; final version received 30 December 2009)

https://www.tandfonline.com/doi/pdf/10.1080/19373261003607972

with the rear wiping angle of change outer panel and the aspect ratio of whole wing. Swing-wing shortcoming is, structure and maneuvering system are complicated, and weight is larger, not quite is fit to aviette and uses

CN203255353U - Variable-sweep wing of aircraft - Google Patents

The utility model discloses a variable-sweep wing of an aircraft. The variable-sweep wing comprises a wing body and two hydraulic clamping devices, wherein the hydraulic clamping devices are fixed on an aircraft body, the wing body is hinged with the aircraft body, a hinge point is positioned...

patents.google.com

 

[Archibald]

Hmmm this thread is going straight ahead and full speed into a brick and concrete massive wall...

View: https://www.youtube.com/watch?v=tMDFv5m18Pw

 

[overscan (PaulMM)]

@MIRAGE 4000 I suggest you don't pick a fight with @aim9xray I know exactly who he is and (some of) what he's done, and you can trust his statements. Also your sources aren't terribly relevant to the points raised, they are very generic and in one case actually undermine your argument when read.

The F-14A was a maintenance hog in the early 2000s for various reasons not specifically related to the swing wing. There were a lot of developments in avionics reliability between the late 1960s and the late 1970s and the F-14A was on the wrong side. The avionics were also very complicated in order to achieve the capability level demanded.

The F-14A engines were older technology and less reliable than the F404. The F-14 airframes were older than the F-18s - like people, older airplanes need more work.

The ultimate verification of the 'swing wing' for the F-14 mission is that the Lockheed Martin Naval ATF design designed in the late 80s/early 90s as its successor included a swing wing as did several AF/X studies afterwards. Variable camber and strakes certainly improve fixed wing performance in some areas, but they don''t make the VG wing redundant, in some situations it could still make sense today depending on mission requirements.

 

[overscan (PaulMM)]

I'd also suggest that you think more about the F-14 mission. Its not an F-15 that happens to live on a carrier. It has different missions, which drive different decisions about configuration.

The North American VFX actually featured leading edge extensions on a fixed wing, but even NA didn't really expect it to have a chance in the competition, they used it mostly as an opportunity to help refine their FX design.

 

[Mirage4000]

@MIRAGE 4000 I suggest you don't pick a fight with @aim9xray I know exactly who he is and (some of) what he's done, and you can trust his statements. Also your sources aren't terribly relevant to the points raised, they are very generic and in one case actually undermine your argument when read.

The F-14A was a maintenance hog in the early 2000s for various reasons not specifically related to the swing wing. There were a lot of developments in avionics reliability between the late 1960s and the late 1970s and the F-14A was on the wrong side. The avionics were also very complicated in order to achieve the capability level demanded.

The F-14A engines were older technology and less reliable than the F404. The F-14 airframes were older than the F-18s - like people, older airplanes need more work.

The ultimate verification of the 'swing wing' for the F-14 mission is that the Lockheed Martin Naval ATF design designed in the late 80s/early 90s as its successor included a swing wing as did several AF/X studies afterwards. Variable camber and strakes certainly improve fixed wing performance in some areas, but they don''t make the VG wing redundant, in some situations it could still make sense today depending on mission requirements.

Correct no one is saying he has not or has has done things, that was not my point.

My point was variable geometry wings while achive some advantages do have disadvantages.

Why Variable Sweep? Pros • Adjustable span for cruise efficiency • Reduced wave drag • CLmax at lower AoA • Trailing edge devices don’t lose effectiveness • Low approach speed • Versatility in mission

Cons • Complexity • Number of moving parts • Weight of support structure • Other options

http://www.dept.aoe.vt.edu/~mason/Mason_f/F14PresS07.pdf

I never said the F-14 was falling from the sky due to the wing box, pivots or related mechanisms but there were troubles.

The U.S. Navy discovered a crack in the center wing section of an F-14 Tomcat fighter and engineers are trying to determine if it is an anomaly or the sign of a larger problem in the fleet of the aging planes.

Navy finds crack in F-14 wing section | Aviation Week Network

The U.S. Navy discovered a crack in the center wing section of an F-14 Tomcat fighter and engineers are trying to determine if it is an anomaly or the sign of a larger problem in the fleet of the aging planes. "It is currently under investigation," a Navy spokesman told The DAILY. "A crack was...

aviationweek.com

As you said the aircraft aged and therefore it required more maintainance.

The question was why do not build more F-14 if the swing wing fighter was better than a fixed wing one.

The VFX Proposal Offering The Grumman VFX proposal showed a wing carry through box somewhat similar to the F-111A configuration at the pivot, except that the main structure was much more geometrically complex.

The wing box structure, which was initially called the “wing carry through box” had a name change in mid 1969. It became known as the Wing Center Section, or WCS. This was a public relations move by Grumman to distance itself from the F-111A wing carry through box, which at the time was in the news receiving bad press for having failed its structural tests related to TIG (Tungsten Inert Gas) welding of D6AC steel.

The test specimen was statically tested and provided some further encouragement that the approach would be successful. This was the first time that a major structure was using welds in tension as part of its basic design. This structure was later fatigue tested using what was thought to be a severe spectrum. After surviving its intended life, the loads were increased 12% to cut down the test time. Eventually the structure failed at a tool mark in the lower skin.

. A more mature and updated mock-up is shown in Figure 9, including all the fuel systems provisions. Note that the access holes do not have a series of small holes drilled into the beam web to attach the fuel cover. This was intentional, since the F-111A wing carry through box had cracks at these small holes and resorted to interference tapered bolts to fix the problem at great cost and complexity. Grumman’s approach was to use clamp-on covers with a built-in groove “Parker” seal to provide fuel tank integrity.

The Development of the F-14A Wing Center Section by Carlos A. Paez, August 2008 the senior Project leader for stress, Dick Cyphers was Project Engineer and Nat Kotlarchyk was his assistant for Analysis, together with Ron Heitzmann who was the Materials and Process Project Lead. These three really run the vehicle engineering airframe part of the program. The Go-Ahead The go ahead to Grumman for the F-14A came in mid January, 1969. Even though this was a big accomplishment, most people realized that while this was a great win, it was also the start of a long, intense, difficult and challenging development effort. Larry Mead (an ex- structural analyst going back to the F-4 Wild Cat and many years later to become one of Grumman’s VP of Engineering) was asked to oversee the overall manufacturing development of the wing carry through box. His principal aim was to make sure the structure could be produced. I.G. (Grant) Hedrick, VP of Engineering looked after the structural integrity of the design. Larry Mead started his reviews with weekly meetings of all concerned. Al Hallock asked Carlos Paez to represent the design effort and to prepare simple sketches and or drawings to illustrate what was being address each week by the engineering team.

https://www.slideshare.net/CarlosPaez25/the-development-of-the-f14a-wcs８０１０８

My whole point is and was there was no need for variable geometry aircraft because they have structural limits and fixed wings are simplier to design, the manuals will allow technicians to avoid accidents but when an airframe ages they retire it, the F-14 swing wing brings an extra element fixed wings do not have so fixed wings are reducing maintainance.

See that Carlos Paez is an engineer from Grumman

Now see

During flight, any maneuver that causes acceleration or deceleration increases the forces and stresses on the wings and fuselage. Stresses on the wings, fuselage, and landing gear of aircraft are tension, compression, shear, bending, and torsion. These stresses are absorbed by each component of the wing structure and transmitted to the fuselage structure. The empennage (tail section) absorbs the same stresses and transmits them to the fuselage. These stresses are known as loads, and the study of loads is called a stress analysis. S

http://home.iitk.ac.in/~mohite/Basic_construction.pdf

The question is simple why F-14 stoped manufacture in 1991, was retired in 2006 and F-15 continues in production even in 2021?

As i said in my personal opinion both F-15 and F-18 having a fixed wing reduced maintainace, price at the expense of a higher landing speed or landing run.

“Back in the 1960s there was a need to vary the airplane’s geometry,” says Captain Don Gaddis of Naval Air Systems Command, a former Tomcat pilot and current program manager for its replacement, Northrop Grumman’s F/A-18 Hornet. On the F/A-18, “we’ve learned how to optimize the wing design so that the aircraft can carry out its functions” without changing geometry.

Swing Wings

It's all done with computers (and good old-fashioned hydraulics).

www.airspacemag.com

but okay let us leave it here, each one will keep its opinion and we should not force our opinions on others.

regards

 

[Nik]

As ever, an educational thread.

Like the 'mercenaries' rule states, everything is air-droppable once: Difference is Carrier and rough-field aircraft do it for a living...

I've just enough 'engineering' instincts to suggest they should have looked much harder at a big-canard delta with growth potential for bigger engines.

But, as I understand it, swing-wing was the only practicable way at that time to get 'fast+high' plus 'low+slow' with available engines...

 

[Fluff]

I give up debating with you on the subject as you keep repeating the same things without taking into consideration what multiple contributors are trying to explain.
Have a nice day.

View attachment 658195

Try to be honest see theses sources

The last flight of the F-14 Tomcat in US service took place October 4, 2006, with the final flight retirement ceremony on September 21, 2006. Two F-14’s were readied for the ceremonial final flight; after the primary plane experiencing mechanical problems, a backup was flown instead. The failure was a reminder of one of the reasons for the retirement, high maintenance costs. The F-14 Tomcat was officially retired on September 22, 2006 at Naval Air Station Oceana. The F-14 fleet is mothballed at the Davis-Monthan “Boneyard.”

Grumman F-14D Tomcat – Prairie

The initial acquisiton cost of an F-14 is quoted by the US Navy at around $38 million. However, the primary disadvantage of the aircraft is not its purchase cost but maintenance expenses. As discussed previously, the life-cycle costs of operating and maintaining an aircraft far exceed the initial acquisition cost. These costs only grow as planes age and require increasingly more maintenance hours per flight hour. This trend has hit the F-14 harder than most of its contemporaries because of its complex airframe (including the variable-geometry wings) and harsh salt-air environment at sea. The F-14 is currently the most expensive aircraft to operate in the Navy inventory, requiring 40 to 60 maintenance manhours per flight hour. For comparison, the F-18 Hornet requires only 20 hours of maintenance and the latest F-18E/F Super Hornet requires just 10 to 15 hours. These high maintenance costs played a large role in the Navy's decision to move the retirement of the F-14 up from 2010 to 2006.

Aerospaceweb.org | Ask Us - F-14 History and Performance

​

Maintenance Upgrades​

One of the most common justifications for a new design aircraft is that the existing one is too maintenance intensive (even though it was undoubtedly considered a vast maintenance improvement over its predecessor!). Consider the F-14 Tomcat and its replacement, the F-18 Hornet. No one had any real performance issues with the F-14 Tomcat but it was considered to be too maintenance intensive.

Maintenance Upgrades

One of the most common justifications for a new design aircraft is that the existing one is too maintenance intensive (even though it was u...

navy-matters.blogspot.com

The decision to incorporate the Super Hornet and decommission the F-14 was mainly due to high amount of maintenance required to keep the Tomcat operational. On average, an F-14 required nearly 50 maintenance hours for every flight hour, while the Super Hornet requires five to 10 maintenance hours for every flight hour.

This Was the Last Time the U.S. Navy's F-14 Tomcat Went to War

A sad story?

nationalinterest.org

The question is you do not want to see the variable geometry wing was one of the main reason it had a very high need for maintainace and that killed the further production and deployment of F-14 besides it was too expensive

Sorry but I'm a firm beleiver that the reasons to change are written after the change. So F18 is smaller = fit more on a ship than F14. F18 has fixed wings, must save a fortune on checking those swivel points. F14 was 'unafordable' seemed pretty affordable when we bought them?

A new aircraft, with the latest tech, especially in the 60's to 80's period, will have moved quite a bit, especially in electronics, so less valves, less moving parts, more LRU's. So yes, less maintenance.

And as the only aircraft available, the Navy settled for more and better F18's.

Most of those improvements could have been engineered into F14's either rebuild or newbuild. But what was the mood in congress, if it was anti-cost, then saying your buying a more affordable aircraft, may have got all those F18's signed off.

 

[Archibald]

I've just enough 'engineering' instincts to suggest they should have looked much harder at a big-canard delta with growth potential for bigger engines.

Not a bad idea, but landing that even on a Nimitz... computers control and FBW would be better if not necessary. And in the 60's, they were in infancy (although the Lunar Module showed the way).

Although the Skyray did fine, so maybe my point is moot.

 

[aim9xray]

in hindsight, knowing what we do now after years of experience and knowledge
how would you have re-designed the F-14 back then if you could have the chance. what would you change if anything?

Good question. Realize first, that the F-14 was designed by very smart people using the the best technology, materials and electronics of the mid-1960s. Also realize that Grumman had little control over the Navy requirements and how the Navy thought they were going to use their new fighter, nor the perceived threat environment. Grumman also had no control over the selection of the TF-30 nor the usage of the Phoenix AMCS or the AIM-54 missile. There was a very short time between Contract award and First Flight (IIRC) which left little or no time for prolonged subsystems development. Even so, the CSDC (Computer Data Signal Converter) and the SDDI interface (pre-dating the MIL-STD-1553 databus by years) were bleeding edge technology at the time.

But, comparing the F-14A as it rolled out in 1969 to a Block II F/A-18F of today is like comparing a Block II Apollo Command Module to a SpaceX Crew Dragon.

Getting back to the F-14, some of the "best practices" of the time turned out to have not held up well. Honeycomb structures were a darling of the 50s and 60s. Both the F-14 and F-15 programs found that honeycombs did not hold up well over time (20+ years of use), suffering delaminations (sometimes catastrophic on the F-15 with stabilators disintegrating in flight). F-14 pioneered in the use of boron composites (stabilator skins) -which have been long since supplanted by other materials.

But how should have things been done? A consistently funded block/model upgrade program would have gone a long ways to improving the Tomcat and reducing maintenance requirements. Look at the E-2 program, for example. Anecdotally, the E-2A was barely usable in the fleet due to radar and computer performance and reliability. The E-2D of today is highly regarded after almost 60 years of continuous improvement. And, in fact, Grumman did have a growth path with the TF30 engine being replaced in the [then] F-14B and much of the avionics in the [planned] F-14C. That went by the wayside with the contractual difficulties of the mid-1970s when the future of the program (and Grumman) was in doubt.

As it was, in-service improvements were frequently deferred or rejected when a SOF (Safety of Flight) issue came up and a fix needed to be funded. Year after year, the number one request from the OAG (fleet Operational Advisory Group) was to add an APU (as the Hornets and Vikings had) so the F-14 could self-start on the carrier deck without external equipment. Never happened, not when there was a high-priority ALR-67 upgrade or something else that needed doing. Other maintenance headaches could have been rethought such as ECS/cooling air to the avionics, wiring/connector issues, WRA racks (and again cooling and wiring/connector issues) - the F-18 program (Navy, MacAir, and Hughes) learned from these and went a different direction. But the time to implement this sort of thing is during a major block change involving remanufacturing the aircraft, not in-service as an AFC.

------

In short, change the programatics. Look at the long-lived programs in the US - C-130, F-15, F-16. The key to improving those Weapon Systems has been to keep them in production so that production money can fund improvements. Once an airplane goes out of production, any improvements come out of operations and maintenance money (OM,N, in the F-14 case) and have to fight with spare parts and gas for priority. (It doen't help that Congress will make cuts in O&M topline money - sometimes in the $billions without regard to what bottom line flow down effects of these cuts.) Non-the-less, some F-14 WRAs were replaced on a cost-saving basis; the F-14A/B CSDC/R and and VDIG/R were notable successes (the MTBF of the original boxes having declined over 30 years to the very low single digits). The DFCS retrofit was another success story.

But there were some things that were never fixed. Late in life, two F-14s were lost in unique mishaps. One crashed on launch when the catapult launch bar (on the nose gear) failed during the catapult stroke. A second airplane went into the water when the steel tailhook shaft failed during arrestment. Neither failure had been seen before in the history of the program. I don't recall the root cause of the launch bar failure, but the tailhook shaft (a steel tube, to save weight) failed due to stress corrosion on the inside surface of the almost 30-year old part). There were no design deficiencies in the parts. Rather than spend the [non-existent] money on reprocuring and replacing these parts, the decision was made to add a permanent recurring (every 25 flight hours) inspection to both components. There was no dollar cost to the F-14 OM,N accounts, but this did cause an incremental increase in maintenance man hours expended which came out of the hides of the maintainers. I am not criticizing this decision - there were additional factors involved; I am just observing out how certain pragmatic tradeoffs can have other consequences.

An everyday equivalent would be the ongoing maintenance costs of your [hypothetical] 1968 Corvette (it's paid for, but you have short oil change intervals, spark plugs & points to replace often, tune-ups, clutch wear, tires etc - coming out of pocket money) - or you could junk it and buy a new new 'vette with electronic ignition, long-live oil, etc (starting at $59K+ capital cost).

This doesn't exactly answer your question, but I hope that this will give you some insight on how things work[ed] in aerospace.

 

[aim9xray]

this is a museum of aviation thus you can consider it a good source.

I worked on the F-14 program for about 18 years in an engineering capacity. I had full flightline access in the course of my duties and dealt with the maintainers and officers. I attended and participated in many contractor/customer engineering management meetings dealing with F-14 software, structures and fatigue life.

By your logic (above), you can consider me a good source.

an anonymous source can not be a reliable source, regardless where you worked, more people worked in the program, and more papers give a clearer view, the document i gave you is based upon scientific research give me proof of your identity and your documents published by a scientific and industrial well stablished intitution to back you up, at this moment you have no way to proof you credentials.

Even If you worked, you need to present offical papers that atest your veracity, the documentation by a museum and an aerodynamic study are enough to support a view.

Quite so. This is the internet, I could be a dog typing at the keyboard and you would not be the wiser.

In fairness, I would ask that you apply the same critical research standards and investigation of qualifications of the unidentified copywriter at "an aviation museum*" and your blog quotations and Wikipedia resources**, OK?

@Mirage4000, you seem passionate about your interest in aerospace. Good! But please research deeper and try to dig down to source material (i.e. Grumman papers - good) rather than present day blog entries (opinion!) and Wikipedia writeups. Do that with passion, understanding, a open mind and a willingness to learn and you will go far.

Returning to the topic at hand, it was always my impression that the 303F was cooked up as a strawman design to show how the 303E with the VG wing was the superior design. You and I have no idea (and never will) if any of the designers had "their finger on the scale" (or not), in able to make the fixed wing come out worse in comparison to VG. I think that it is telling that all of the other publicly released Grumman Model 303 designs 303-60 to 303G have variable sweep wings.


*the discussion at the Prairie Air Museum has not been updated in 14 years.
**the discussion pertains specifically to a Supersonic Business Jet design exercise for high altitude supersonic cruise of 1.6 Mach and and implied load factor of no more more than 3 (probably 2.5). No requirements for Mach 2+ flight, external stores carriage, in-flight refueling, sub/supersonic air combat maneuvering at up to 7.33g nor carrier compatibility are mentioned. It would appear that the stated design trades in this study are specifically related to this design only.

 

[Mirage4000]

this is a museum of aviation thus you can consider it a good source.

I worked on the F-14 program for about 18 years in an engineering capacity. I had full flightline access in the course of my duties and dealt with the maintainers and officers. I attended and participated in many contractor/customer engineering management meetings dealing with F-14 software, structures and fatigue life.

By your logic (above), you can consider me a good source.

an anonymous source can not be a reliable source, regardless where you worked, more people worked in the program, and more papers give a clearer view, the document i gave you is based upon scientific research give me proof of your identity and your documents published by a scientific and industrial well stablished intitution to back you up, at this moment you have no way to proof you credentials.

Even If you worked, you need to present offical papers that atest your veracity, the documentation by a museum and an aerodynamic study are enough to support a view.

Quite so. This is the internet, I could be a dog typing at the keyboard and you would not be the wiser.

In fairness, I would ask that you apply the same critical research standards and investigation of qualifications of the unidentified copywriter at "an aviation museum*" and your blog quotations and Wikipedia resources**, OK?

@Mirage4000, you seem passionate about your interest in aerospace. Good! But please research deeper and try to dig down to source material (i.e. Grumman papers - good) rather than present day blog entries (opinion!) and Wikipedia writeups. Do that with passion, understanding, a open mind and a willingness to learn and you will go far.

Returning to the topic at hand, it was always my impression that the 303F was cooked up as a strawman design to show how the 303E with the VG wing was the superior design. You and I have no idea (and never will) if any of the designers had "their finger on the scale" (or not), in able to make the fixed wing come out worse in comparison to VG. I think that it is telling that all of the other publicly released Grumman Model 303 designs 303-60 to 303G have variable sweep wings.


*the discussion at the Prairie Air Museum has not been updated in 14 years.
**the discussion pertains specifically to a Supersonic Business Jet design exercise for high altitude supersonic cruise of 1.6 Mach and and implied load factor of no more more than 3 (probably 2.5). No requirements for Mach 2+ flight, external stores carriage, in-flight refueling, sub/supersonic air combat maneuvering at up to 7.33g nor carrier compatibility are mentioned. It would appear that the stated design trades in this study are specifically related to this design only.

Aircraft are multidiciplinary endevours.

A fly hour price will influence as much as an advanced radar.
Aircraft are designed by thousends of people, operated by other thousends of people, and financed by millions of people.

I quoted Carlos Paez a Grumman engineer who worked on the F-14 wing center section as well as Captain Don Gaddis of Naval Air Systems Command, a former Tomcat pilot.

The F-14 as a low speed short landing run aircraft was excellent.

Grumman never lied when they said the fixed wing had inferior low altitude and low speed performance.

However aircraft are like women, if you marry a woman with blue eyes you can not marry another with hazel eyes, what I mean each aircraft has advantages and disadvantages, the choice will be prioritize your needs.
to exemplify read the next website where the Israelies say why the picked the F-15 over the F-14, basicaly they say the F-14 struggled against the A-4 and it was a BVR aircraft, that was result of Variable geometry wing with low thrust to weight ratio

IAF Fighter Pilots Explain why Israel Picked the F-15 Eagle over the F-14 Tomcat - The Aviation Geek Club

IAF Fighter Pilots Explains why Israel Picked the F-15 Eagle over the F-14 Tomcat. From an Israeli point of view, the Tomcat could not match the Eagle

theaviationgeekclub.com

As such the Variable geometry aircraft offered better performance for landings even having inferior handling at 700-1200 km/h or higher maintenance requirements.

But the F-14A was the best solution to do most of things as a compromise.

Later aircraft prioritized different aspects.

On MiG-29 dogfighting capability and price meant as naval fighter was not as good at landing as F-14 was.

When F-14 aged, it was not its quality what mattered, definitively it was a really good aircraft, new built aircraft with upgrades could have done things better in some sense better than F-18E, but as i told you at the begining, finance was another factor, so it was better to deploy F-18 even the US navy lost some advantages F-14 had as long as money was saved.

Fixed wings give less trouble due to simplier structure, that translates well when maintenance is important, but as landing speed is concerned it is harder to harmonize the need of high aspect ratio for landings with low aspect ratio for high speed.

As such is not that F-14 is better than F-18 or F-15, it was just a matter what was prioritized, Grumman never lied in terms of what they asked to them to do, but if the requirements were less maintenance, price and simplicity, well they were wrong and the proof is F-18 and f-15 continue in production almost 50 years after their first flight while F-14 stopped production in1991.

Regards

 

[F-14D]

For the record, the F-14D went out of production because Dick Cheney and DoD ordered it out of production and directed the Navy to develop a new aircraft based on the F/A-18. This was not the Navy's choice as at that time they planned that versions of the F-14 would be the Navy's primary fighter (and probably strike fighter) until 2015.

 

[SSgtC]

For the record, the F-14D went out of production because Dick Cheney and DoD ordered it out of production and directed the Navy to develop a new aircraft based on the F/A-18. This was not the Navy's choice as at that time they planned that versions of the F-14 would be the Navy's primary fighter (and probably strike fighter) until 2015.

That still pisses me off. I'll never understand Cheney's God damn hate-boner for Naval Aviation in general and the Tomcat in particular. That man singlehandedly screwed the Navy's carrier air wings all the way up until today. If it wasn't so f*****g maddening, it would honestly be impressive

 

[helmutkohl]

For the record, the F-14D went out of production because Dick Cheney and DoD ordered it out of production and directed the Navy to develop a new aircraft based on the F/A-18. This was not the Navy's choice as at that time they planned that versions of the F-14 would be the Navy's primary fighter (and probably strike fighter) until 2015.

what was Dick's official stance?
and was he on the Boeing/McD payroll at that time?

I remember during the 2004 US election, Zell Miller (a Democrat who supported Bush). tried to blame Kerry as the cause of the loss of the F-14.

 

[F-14D]

It would look like a F-15B except with TF30 engines that suck. Maybe it would motivate the USN to provide better engines ?

The F-14 was never intended to go into production with the TF30s, they were just for the early few F-14s to speed development of the aircraft However reliability and cost problems with the F401 (a derivative of the F100 that was supposed to be the production version for the Tomcat) forced the Navy to stay with the TF30 until the arrival of the superb F110. Until the F110 there were no better engines for the USN to provide. The Navy simply wasn't going to be provided the funds necessary to develop a new engine on its own.

 

[helmutkohl]

it would have been nice had the timing of the F110 and F-14s been better. would have made a great hi-lo mix with the F-16 for some countries.
I think Pre REvolution Iran could have been a possibility as they were also thinking of the F-16 to go with the F-14

 

[Mirage4000]

For the record, the F-14D went out of production because Dick Cheney and DoD ordered it out of production and directed the Navy to develop a new aircraft based on the F/A-18. This was not the Navy's choice as at that time they planned that versions of the F-14 would be the Navy's primary fighter (and probably strike fighter) until 2015.

The question is no politician makes a decision like that without justifying it.


The F-14A with TF-30 was more expensive than F-15 as a fighter and much less capable in dogfights than both F-15 and F-18.

So in the 1970s the already more expensive F-14A than the F-15, needed to start production beyond the first batch of 60 aircraft, why? well if they would have waited for the better engine it would had mean more money and a delay, thus the F-15N meant an extra price and the F-14B another delay and a more expensive price.


As compromise was to build most of them as F-14A.

In the 1990s, the program was cancelled because the F/A-18 was much more affordable and its technologies allowed good landings and take off performance.

F-18E was deemed as a much cheaper aircraft than F-14A, the reality was F-14B was expensive to operate, maintain and keep, its export sucess was another factor.

F-15 was exported to more countries and with higher numbers allowing for more countries buying it.

Thus indeed F-14D or F-14B were good aircraft, the reality price was the factor that killed the program, it never offered a superior fighter to F-15 in the export market, niether AIM-54 was so capable since many smaller more agile aircraft started to threat aircraft carrier groups.

Then just by price the F-14 program was terminated

ich would not be available in time for initial production. In order to get the aircraft quickly to the fleet, the Naval Air Systems Command sanctioned a modified version of the F-111B engine for use in the Tomcat. This engine, the TF-30-P-4l2, would be installed in only the first 67 F-14s until Pratt &: Whitney delivered its new Advanced Technology Engine in 1970 [

At the end of the F-14A production cycle, it was assumed that the new F-401 ATE would be ready. Plans called for 643 more aircraft to be produced with the new engine [Ref. 35. 1] . These aircraft would be the F-14B model. Pratt and Whitney was unable to deliver the F-401 ATE in 1970. As state of the art technology, the F-401 ATE developed problems in the areas of reliability, endurance, and ability to withstand rapid throttle movement. By 1971, the Office of the Secretary of Defense had reduced the planned number of F-14s to 301 because of technical problems and cost overruns in the F-401 ATE program. [Ref. 35. 2]


As problems continued to mount for the Advanced Technology Engine, the Navy continued to push back the expected delivery date for the F-401 ATE. Eventually, the Navy concluded that the cost of bringing the F-401 ATE to an acceptable level of reliability and performance was prohibitive. In March of 1974, the Navy decided to terminate the F-401 ATE program. When the F-401 ATE program died, so did the F-14B and followon programs. [Ref. 35. 3J


estimated that the 12 F-14D aircraft scheduled for production in FY 89 would cost the government nearly $75 million each. This cost was three times greater than the $23 million price paid for the Navy's other carrier-based fighter, the F/A-18 Hornet. [Ref. 36. 4]

Grumman offered the Pentagon long term price guarantees, in April of 1991, on the F-14D and F-14 derivatives in an attempt to get the aircraft into the FY 92 Budget. In a letter to Cheney, the Grumman Aerospace Corporation Chairrr,an, Renso corporali, attempted to price competitively the F-14 against the F/A-18E/F. He also committed Grumman to broad development of the F-14D Quick strike, an F-14D derivative with added air-to-ground attack capabilities. Corporali's offer · ... as seen as a last ditch effort on the part of Grumman to reopen the partially closed F-14 production line. [Ref. 63. 24~ Although the proposal sounded promising, Navy officials questioned whether Grumman would be able to hold to its stated rates and prices. In the end, the proposal was rejected by This effectively signalled the end of Grumman's F-14D program

https://core.ac.uk/download/pdf/36723663.pdf

 

[Archibald]

it would have been nice had the timing of the F110 and F-14s been better. would have made a great hi-lo mix with the F-16 for some countries.
I think Pre REvolution Iran could have been a possibility as they were also thinking of the F-16 to go with the F-14

Wait, is that F-16 picture true or fabricated ? I mean, where the Shah F-16s that close from delivery ? (I do know they were diverted to Israel IMHO )

It looks sexy as hell in that camo.

 

[overscan (PaulMM)]

it would have been nice had the timing of the F110 and F-14s been better. would have made a great hi-lo mix with the F-16 for some countries.
I think Pre REvolution Iran could have been a possibility as they were also thinking of the F-16 to go with the F-14

Wait, is that F-16 picture true or fabricated ? I mean, where the Shah F-16s that close from delivery ? (I do know they were diverted to Israel IMHO )

It looks sexy as hell in that camo.

It's a plastic model - there's a guy who builds great models and dioramas and takes photos outside in natural daylight.

 

[helmutkohl]

yup its a very great model! Iran never received F-16s

but I remember back in the days this image floated around

 

[Manuducati]

it would have been nice had the timing of the F110 and F-14s been better. would have made a great hi-lo mix with the F-16 for some countries.
I think Pre REvolution Iran could have been a possibility as they were also thinking of the F-16 to go with the F-14

Wait, is that F-16 picture true or fabricated ? I mean, where the Shah F-16s that close from delivery ? (I do know they were diverted to Israel IMHO )

It looks sexy as hell in that camo.

It's a plastic model - there's a guy who builds great models and dioramas and takes photos outside in natural daydaylight

More about the Iranian F-16 purchase and this superb model and diorama:

Image of the General Dynamics F-16 "Fighting Falcon" | F-16A | 3-6591 - Wing's Palette

wpalette.com

 

[Arjen]

Thank you, Manuducati.

To others: Always. Give. Your. Sources

 

[Archibald]

Craaaaap ! To quote "Monty Pythons and holy Grail "

"Kaamelott"

"It's just a model !" ROTFL

Frack, first time I'm fooled this way. Says something indeed, about the diorama quality (and how faking something, even without any malice, has become as easy as making coffee).

no malice, no negative consequences, no resent. Just my mind being blown.

 

[overscan (PaulMM)]

GE's engine for the F-14B was designated F400.

GE Tests Engine
For F-I4B, F-l5

General Electric’s F100/F400 engine entry in the powerplant competition for the Navy’s F-14B and the Air Force’s F-15 aircraft is now undergoing static tests at the company’s Evendale, Ohio, facility.

engine is an augmented turbofan in the 28,000-30,000-lb. thrust class. The General Electric F100/F400 is based on a modified core engine from the GE1 engine family. For much of the development testing, General Electric engineers used the powerful, GE1/10 augmented turbofan, which was incorrectly identified as GE’s entry in the F-14B/F-15 engine competition (AW&ST Sept. 29, 1969)

 

[Archibald]

Okay, I see... GE entry in the F-15 engine race was yet another member in the extended GE-1 family (that included the CF6, J101, F404 and also the J97 from the Ryan stealth drone, AQM-91 Compass Arrow)