Convair Model 49 Advanced Aerial Fire Support System

[Skybolt]

Moreover, it takes guts to stand up close enough to a moving target like that to have a chance to hit it with an RPG-7. Very near to a suicede attack. During the Soviet war in Afghanistan the mujaheddin tried to ambush Hinds with RPG-7 shot straight level from mountain sides. Soviets started to take real losses only after CIA provided Stingers.

 

[Jemiba]

Well, I don't want to start a discussion à la "attack helicopter vs. Vietcong", as it would
remain strictly academic (as most other such discussion .. : ), and you're probably right,
that it wouldn't have been an easy target. Actually, not target, that can shoot back is .
But I doubt the mentioned survivability against shaped charged munitions, especially because of
the barrel shape. Hits on conventional aircraft (and to a certain degree maybe on helis, too)
could punch a hole in flying surfaces, but due to the large area, there quite often (hopefully)
would be no structural damage, or damage to vital parts, I think, the effect of the shaped charge
would just heat up the air behind. Just look at all those photos of battle damaged aircraft, where
you can look right through wings or fuselage.
But if hitting such a barrel, the effects with quite a great probability would stride deep into
the structure and I'm sure, that no of the materials could have withstand. It still was designed as
an aircraft,not a tank ! And if I understood those reports correctly, the US Army learned during the
conflicts in Somalia and later Afghanistan and Iraq, that fighting from a heli in a hover is very dangerous,
much more, than from a moving heli. IIRC, this was the explanation for the very different percentages
of damaged Army AH-64 and USMC AH-1.
And this thing was designed exactly to do that !

 

[Abraham Gubler]

But I doubt the mentioned survivability against shaped charged munitions, especially because of the barrel shape. Hits on conventional aircraft (and to a certain degree maybe on helis, too) could punch a hole in flying surfaces, but due to the large area, there quite often (hopefully) would be no structural damage, or damage to vital parts, I think, the effect of the shaped charge would just heat up the air behind. Just look at all those photos of battle damaged aircraft, where you can look right through wings or fuselage.

The Vietnamese rarely used shaped charge warheads in their RPGs. It was mostly HE Frag. But a shaped sharge would not be very effective against the Convair AAFSS and don’t quite work the way you detail.

The Convair AAFSS’s barrel shape provides structural strength not armour resistance. It is a hollow barrel, actually an annular wing (ring shaped) so any penetrator would pass through this wing and then into the air on the other side. A shaped charge jet would actually punch through the armour plate and then ‘spray’ into the area beyond unless it was more dense material. The shaped charge jet would be severely disrupted by the dual hardness layered armour but would still cause a lot of damage to an engine or fuel tank. But the jet’s effect would then be finished.

The holes punched in wings that you mention are from solid bullets and through the very thin aluminium used by weight conscious aircraft designers. Such bullets would just dent the steel armour of the Convair AAFSS.

And if I understood those reports correctly, the US Army learned during the conflicts in Somalia and later Afghanistan and Iraq, that fighting from a heli in a hover is very dangerous, much more, than from a moving heli. IIRC, this was the explanation for the very different percentages of damaged Army AH-64 and USMC AH-1.
And this thing was designed exactly to do that !

The US Army learnt that engaging the enemy from a hover was not a good idea in Vietnam! I don’t think any of the helicopters in Somalia were hovering when they were shot down. Black Hawk Down is pretty clear on this – they were flying racetracks. Hover attacks in Iraq and Afghanistan are usually long range attacks using the attack helicopters fire control system (AAFSS was the first helicopter to be designed with a fire control system) to engage the enemy from outside their situational awareness.

However fighting from a hover was only one of the Convair AAFSS modes, along with landed – a unique capability and one that opens up many CSAR opporunities. It could also fight from forward flight with all weapons. Also while in hovering mode it could presumably fly forwards, backwards and to the sides. Unlike conventional helicopters this type of design could fly just as well in any of these directions.

With the rotors encapsulated in the annular wing it could hover in amongst or very close to trees and terrain. Like the Israeli UrbanAero and the Hiller flying platforms. This would enable the Convair AAFSS to use terrain for masking far better than conventional helicopters. Move the sighting unit to above the crew position and you have an idea platform for shooting guided missiles from behind cover.

 

[Abraham Gubler]

Moreover, it takes guts to stand up close enough to a moving target like that to have a chance to hit it with an RPG-7. Very near to a suicede attack. During the Soviet war in Afghanistan the mujaheddin tried to ambush Hinds with RPG-7 shot straight level from mountain sides. Soviets started to take real losses only after CIA provided Stingers.

Not to mention the RPG was not the anti-aircraft weapon of choice by the Vietnamese. It was the 12.7mm DShK heavy machinegun.

There were some 200 AH-1Gs shoot down over Vietnam. While I don't have a full statistical study, a quick reading of 'US Army AH-1 Cobra Units in Vietnam' by Jonathan Bernstein indicates that all bar two were shoot down by 7.62mm and 12.7mm machinegun fire. The other two were shoot down by SA-7s. I do know of two UH-1 Huey gunships shoot down by RPGs with both being head on shoots ("down the throat"). AH-1 armament was upgrade to the 20mm gun expressly so it could outrange the 12.7mm HMG.

Apart from its massive increase in fire suppression and manoeuvrability compared to the AH-1G the Convair AAFSS would have been effectively invulnerable to 12.7mm HMGs.

 

[AeroFranz]

I am not convinced that you could harden the AAFS and make it a viable VTOL at the same time.
In order to take off with two engines operating, with a margin for maneuver (T/W~1.2), in hot and high conditions, you would have to make the thing grossly overpowered when operating on all engines. That means in normal operations its engines are seldom operating at optimum RPM, with consequent SFC penalty. Then it means you have to carry more fuel, which means more power, more weight, and so on and so forth.
Just like any other VTOL, each pound of extra weight in armament or fuel costs you several times as much in takeoff gross weight. Unlike other VTOL platforms (even helos), you can't perform a rolling takeoff and gain some translational lift in a tailsitter (this practice was common in Vietnam).

So, can you make a flying tank? sure. Only, because of the armor and built-in redundancy it can carry fuel OR weapons.
And both endurance and payload carrying capabilities are vital attributes of COIN...

 

[Abraham Gubler]

I am not convinced that you could harden the AAFS and make it a viable VTOL at the same time.
In order to take off with two engines operating, with a margin for maneuver (T/W~1.2), in hot and high conditions, you would have to make the thing grossly overpowered when operating on all engines. That means in normal operations its engines are seldom operating at optimum RPM, with consequent SFC penalty. Then it means you have to carry more fuel, which means more power, more weight, and so on and so forth.

Well there is no evidence to suggest it had a two engine VTOL requirement (though it is likely). Also thanks to the hugely different thrust required for takeoff and in flight one can assume something like one engine conventional flight, two engine high angle of attack flight and three engine hover? But if there is a one engine out vertical takeoff requirement what are the numbers?

Quickly using the McCormick thrust loading formula the Convair Model 49’s propellers and engines (three LTC4B-11s able to produce 3,400 lbs each) should be able to generate around 35,284 lbs of thrust (taking into account an additional 20% efficiency thanks to the ducted fan). The Model 49 is very heavily thrust loaded compared to a conventional helicopter. Meaning maximum takeoff weight of the Model 49 (with the manoeuvre margin) should be about 13 tons (29,403 lbs).

For hovering weights an important factor is the ferry requirement. That’s 8,100 pounds of additional, external fuel (four 300 gallon tanks) that must be lifted from a tail sit. Considering a typical weapons payload is about 3,000 pounds (six TOW missiles, 1,000 30x113mm, 500 40x53mm, 12,000 7.62x51mm) that’s a tactical payload surplus of 5,100 pounds. Meaning with full internal fuel and weapons the Model 49 would weigh around 24,300 lbs which is LESS than the thrust generated with only two engines (25,111 lbs). More weight than the 80% of thrust needed for manoeuvrable VTOL but enough to keep it in the air on takeoff if it looses a donk.

So the Model 49 would have a two engine emergency hover capability in its typical payload. For one engine out safety for ferry takeoffs some kind of quick release for the external tanks could provide a solution.

Just like any other VTOL, each pound of extra weight in armament or fuel costs you several times as much in takeoff gross weight. Unlike other VTOL platforms (even helos), you can't perform a rolling takeoff and gain some translational lift in a tailsitter (this practice was common in Vietnam).

As to the rest of the Model 49’s weight breakdown compared to a more conventional VTOL it has the advantage of using exactly the same power and aerodynamic configuration for vertical takeoff and landing as it does for forward flight. So there is no wasted weight for changing the aerodynamic surfaces or thrust direction in order to transition.

The only ‘extra’ weight is a very simple hydraulic jack to lower the crew compartment. Since this configuration change has nothing to do with the aerodynamic and thrust components it can be as complex as the millions of hydraulic actuators in use around the world in bulldozers and forklifts. A drop in the ocean of engineering complexity compared to tilt rotors, tilt props, vectored thrust, swing wings, gyro stabilised hingeless rotors, twisting anti-torque rotors, etc.

 

[yasotay]

A very interesting discussion. The tactics have to fit the situation. Hovering tactics came about as the U.S. Army focused on the Fulda Gap and looked to take sniper shots (in er... mass) at the Soviet juggernaut. These tactics worked in Desert Storm as well because the enemy was obliging enough to let us do that. The terrain helped also of course. Somalia was the first opportunity to have to deal with a tactical situation that required a return to other tactics. The Blackhawks were indeed in a slow orbit when they were hit but they were not traveling at tactical cruise either. Today the tactics remain a variance of the same used in Vietnam.

Statistically the prime threat to helicopters remains the gun, although RPG and MANPADs are increasing. "Speed is life" remains a valid maxim for low flyers.

As to the AAFSS speed would certainly have made it a harder RPG target. However its speed would have made it almost a CAS platform as far as engagement times, (might not have been able to fire as close to friendlies as a helo has been able to) so there would have been trade-offs. As to what happens if a RPG hit the aircraft, it would really depend on where the aircraft was hit. I have seen UH-60 hit by RPG that returned to base. There have been helos brought down by one bullet in the right place.

Oh and I meant to make the comment up front that the Model 49 would likely only have used VTOL for take off and landing in the given scenario. The hard part in SE Asia would have been the take off with a full load of fuel and ammo.

 

[Abraham Gubler]

As to the AAFSS speed would certainly have made it a harder RPG target. However its speed would have made it almost a CAS platform as far as engagement times, (might not have been able to fire as close to friendlies as a helo has been able to) so there would have been trade-offs.

The Convair Model 49 AAFSS is not a conventional aircraft. While it would have a high maximum speed, well over 300 knots, it would also have a very low stall speed. Apart from its ability to hover (speed of 0 knots) it would be able to sustain a very low flight speed using a mix of wing lift and thrust lift. Its stalling speed in this situation would probably be better than the XF5U (Zimmermann low aspect ratio aircraft) and well under 50 knots. No trade off.

Also as I mentioned above thanks to its enclosed rotor it can hover in amongst or very close to the terrain, be it trees, buildings, cliffs, etc. So as for its close air support (CAS) capability it would not be limited in anyway by its high speed. It would be able to go as low and slow as anything else and even more so.

Convair suggested that it could also be a ground combat platform. So it could just land and duke it out toe to toe with the enemy, probably quickly hopping from firing position to firing position. Armed with the 105mm recoilless rifles options it could almost fight on the ground like a tank using terrain to quickly unmask itself, shoot and then drop back to cover to reload. Like a tank on x10 speed that is.

Oh and I meant to make the comment up front that the Model 49 would likely only have used VTOL for take off and landing in the given scenario. The hard part in SE Asia would have been the take off with a full load of fuel and ammo.

As I pointed out above the Model 49 has a very high margin of thrust to combat weight thanks to its ferry fuel load requirement. More than enough to compensate for hot and high conditions. Also the types of engines used are now putting out around 4,600 hp a 35% power growth in the 40 years since it was designed.

Further why couldn’t this aircraft use a rolling takeoff to maximise on wing lift like a Sea Harrier? The assumption is it can’t because it’s a tail sitter. But it has wheels, wings, etc, all it needs is a runway. As I’ve drawn in this diagram attached its more than practical. Add a ski jump at the end for even more boost...

 

[John21]

Does anyone have any information on what the WASP Rocket is/was? It would seem to have to be pretty small if they were thinking about fitting 500 ;D of them in place of another weapon. Still a cool concept, but it seems to be an mechanical nightmare.

 

[Abraham Gubler]

Does anyone have any information on what the WASP Rocket is/was? It would seem to have to be pretty small if they were thinking about fitting 500 ;D of them in place of another weapon. Still a cool concept, but it seems to be an mechanical nightmare.

I asked the same question yesterday that bumped this thread.

Does anyone have any idea what the "WASP Rocket" mentioned in the Convair AAFSS offer is? The limited information says that the centre turret could be equipped with either two 30x113mm cannons with 1,000 rounds for each gun or a single 30mm and 500 WASP rockets. If weight is matched between the options this would mean each "WASP" would weigh about 1kg (2.2 lbs). I would imagine something like the 66mm rocket of the M72 LAW? Google turns up nothing except that the Yugoslavian name for their M72 clone was 'Osa' or 'Wasp'.

If the WASP was something like the M72 66mm or the Microcell 2 inch rocket then a magazine feed launcher would not be such a mechanical nightmare. The trainable launcher would be much, much lighter and simpler than any cannon, just a pointable tube with exhaust venting. The magazine would be more complex but if the rockets were shaped with an even outer mould line like a conventional cannon round it could work. A cylinder of 2-3 inches (51-76mm) diameter, 15-20 inches long (380-508mm) that weighs 2-5 lbs (1-2kg) is about the same size as a 40mm Bofors round. This would be no more complex than the many linkless magazines that feed medium calibre automatic guns.

Assuming the WASP was a magazine feed, air launched version of the M72 LAW then you have a fearsome weapon. Especially if there is a first round selection between different types of rounds. With options like HEAT (M72) able to penetrate 12 inches (305mm) of RHA, incidenary (M74) with 1.34 lbs (0.61kg) thickened pyrophoric agent (TPA), HE-FRAG and other options. These little rockets would be a lot more effective launched from air than from ground. With a burn out velocity of only 290 knots the boost to kinematics from a 220 knot launcher are quite high. However effective range above 1 NM (1.8km) would be ambitious. But the ability to 'walk' on rapid fire rounds (60-120 rpm) from a very deep magazine of HEAT or the 'hotter than naplam' TPA round would be devastating to tanks and infantry.

 

[AeroFranz]

Further why couldn’t this aircraft use a rolling takeoff to maximise on wing lift like a Sea Harrier? The assumption is it can’t because it’s a tail sitter. But it has wheels, wings, etc, all it needs is a runway. As I’ve drawn in this diagram attached its more than practical. Add a ski jump at the end for even more boost...

The ring wing tends to stall at the front lip at high angles of attack, with some nasty pitch-down moments associated with the turning of the flow from horizontal (in the freestream ahead of the duct) to near vertical (in the duct) to horizontal again (in the exhaust).
This is something that was experienced by the VZ-4 Doak (I think that's the designation) and the X-22. This makes transition for ducted fans a little bit touchy. One solution to the lip stall is to put a big radius on the front lip of the duct (see X-22), but it does have an adverse effect on high-speed flight. The nose down moment is taken care by having massive control authority with vanes in the exhaust. I think accellerating down the runway is also going to be hard unless you find a way to turn the exhaust to near horizontal. I don't think the control vanes are designed to handle such deflections. I suspect the turning efficiency would be poor at high angles unless you had a nice, long, gently curving surface. On the other hand, you could probably do 45 degrees.

 

[Abraham Gubler]

I don't think the control vanes are designed to handle such deflections. I suspect the turning efficiency would be poor at high angles unless you had a nice, long, gently curving surface. On the other hand, you could probably do 45 degrees.

The pitch vanes on the Model 49 are huge. They have an area of 112 sqf or more than half of the annular wing/shroud area of 205 sqf. They had a pitch of +- 30 degrees.

Also the propfan of the Model 49 is very different to those of the X-22 and VZ-4. The shroud is much deeper, quartered by the struts and with much, much more thrust and subsequent suction being generated by the propellers. Also what is happening to the turbine exhaust? Is it being injected into the duct? There is no easily identified exhaust vent in the pictures of the Model 49 but the engine covers show that they are mounted at the lip of the shroud.

How will all this effect the flow of air over the annular wing? Anyway the high angle of attack flight option isn't too necessary for the performance of the Model 49. Transition can be a quick process from vertical flight/hover to horizontal flight as in the XFY-1. In horizontal flight a speed regime of 100 to 300 knots would be slow enough for getting close to the weeds and too fast for pintle mount HMG gunners.

 

[Abraham Gubler]

Playing around with some potential evolution of the Convair Model 49 and its applicability to naval basing raises some interesting development. Presumably a naval version without the armour and guns and with radar, sonar and torpedos could be built. As a naval VTOL aircraft in comparison to helicopters the Model 49 offers some significant advantages in a crucial area of ship design: length.

Compared to a conventional helicopter the Model 49 does not occupy less hangar surface area. Two Model 49s (23’x23’) will fit one after the other in roughly the same space as two ~10 tonne naval helicopters (Seahawk: 41’x11’) side by side. However the Model 49 would require a hangar three decks high (30’) compared to the two deck height of the helicopter (20’). So in pure hangar space terms it is disadvantageous. That is except that these hangars have to be located on ships...

Firstly the ship needs a flight deck to operate a helicopter. These have to big enough to encompass the spinning rotor with a decent safety margin. Flight decks are usually up to 50-70’ long and the full width of the ship (40-50’). The Model 49 needs none of this. With its enclosed rotors it just needs enough space to fit on to (25’x25’). It needs far less safety space because any collision would only be at very small speeds (the differential between the aircraft and the ship) compared to the very high speeds of a rotor tip collision (Mach 0.65 for a Seahawk).

One of the most constrained dimensions of a conventional monohull warship is length. Length is one of the metrics used to predict cost and is heavily consumed by weapons (firing arcs) and engines (uptakes, intakes). The DDG-51 was originally designed without a hangar because they couldn’t fit it for the cost limited length. In the length needed for a typical flight deck and hangar to operate two Seahawks (90’-100’) a Model 49 flight deck and three plane hangar can fit (without side by side Model 49s). This is a significant difference. Especially because you could provide a two VTOL flight deck/hangar combination in only 75’ or 50’ if you have enough beam to hangar the VTOLs side by side.

For example on a DD 963 hull a flight deck and hangar for two Seahawks can be provided. Utilising as much space for Model 49s could enable two flight decks and a hangar for up to 10 Model 49s.

 

[Abraham Gubler]

For the Marines this Model 49 is a heart breaker. Because of the enclosed rotor your ability to launch and recover on the flight deck is transformed. An LHD can easily fit 90 (!) Model 49s on deck for launch and recover.

 

[Jemiba]

Great idea, and we shouldn’t forget, that shape and take-off/landing characteristics are making
the Model 49 the ideal aircraft to be based on submarines. A modification of the Ohio SSBN
(drawing from http://www.globalsecurity.org/ )could easily take 6 Mod 49, if a double-storey
hangar could be realised even 12 ! Would be a nasty surprise for, say, Somalian pirates, if a flight
of Mod 49s (it would need an appropriate name of course, maybe “Grizzly II” ?) would roar down
and smash their base, although no US warship was known to be in the vicinty !
Looking like giant soldiers, when in a hover and mowing down every resistance with ease, would
surely have an enormous pyschological effect ! ;D

P.S.: Abraham, it’s time to spill the beans, I think ! You’ve bought the patents and are promoting
the Model 49 on your own now, aren’t you ?

P.S.S.: I reclaim for myself the right for the above mentioned scenario to be used in any fictional
publication (film, book, comic, etc.)

 

[Abraham Gubler]

Great idea, and we shouldn’t forget, that shape and take-off/landing characteristics are making
the Model 49 the ideal aircraft to be based on submarines.

Lockheed did I guess resurrect some of their Convair heritage (now part of Lockheed Martin via Martin Marietta, not General Dynamics) of the XFY with their proposed submarine tail sitter UCAV. Also their was a AIAA contest submission that had a tailsitter for submarine use.

P.S.: Abraham, it’s time to spill the beans, I think ! You’ve bought the patents and are promoting
the Model 49 on your own now, aren’t you ? ;

Nah just thinking about 'what if'. And I'm only posting here the tip of the iceberg... I think this aircraft could have spawned a whole range of options. Tailsitting has only been held back by the difficulties of aligning the pilot's perception with the aircraft's vector. But with something like the articulated nose that problem is solved. And it is a solution that is a lot simpler than tilting rotors and the like for VTOL.

 

[sferrin]

Great idea, and we shouldn’t forget, that shape and take-off/landing characteristics are making
the Model 49 the ideal aircraft to be based on submarines.

Lockheed did I guess resurrect some of their Convair heritage (now part of Lockheed Martin via Martin Marietta, not General Dynamics) of the XFY with their proposed submarine tail sitter UCAV. Also their was a AIAA contest submission that had a tailsitter for submarine use.

Is that something different than Cormorant? ???

 

[Triton]

Convair Model 49

Source: http://www.arcforums.com/forums/air/lofiversion/index.php?t202161.html

 

[sferrin]

Ah hell ya. Six recoiless rifles. I wonder how they reloaded them. ???

 

[Abraham Gubler]

Would cause serious harm - not quite kill - for a copy of the full proposal.

 

[Triton]

Would cause serious harm - not quite kill - for a copy of the full proposal.

You and me both.

 

[Abraham Gubler]

Ah hell ya. Six recoiless rifles. I wonder how they reloaded them. ???

Easy. You land and a tech comes up and opens the breech, ejects the casing and inserts a new round. Which is why there are six rifles rather than one or two. A salvo of six 105mm shells from the air would be a pretty fearsome thing for any VC AA positon or bunker.

 

[Triton]

Anyone have a guess of what the Tri-Service aircraft designation would have been had the Convair Model 49 been built? Would it have been classified as a VTOL airplane or a helicopter? AV-9, AH-56, or a new designation?

 

[Colonial-Marine]

Probably an AV designation. All in all, that must have been a hefty work-load for one pilot. Certainly one of the most radical proposals for any program I've seen. Crazy 1960s.

 

[Abraham Gubler]

Does anyone have any information on what the WASP Rocket is/was? It would seem to have to be pretty small if they were thinking about fitting 500 ;D of them in place of another weapon. Still a cool concept, but it seems to be an mechanical nightmare.

Here are some pictures. Apparantly a revovler launcher for rockets feed by a hopper.

 

[Abraham Gubler]

Probably an AV designation. All in all, that must have been a hefty work-load for one pilot. Certainly one of the most radical proposals for any program I've seen. Crazy 1960s.

And you've flown one? You've flown anything?

The Model 49 would be easier to fly than a helicopter because despite looking quite odd its just a conventional aircraft.

Technically its not a helicopter because lift is not generated by a rotating wing. However I'm sure the US Army would have called it whatever they wanted to.

 

[yasotay]

Probably an AV designation. All in all, that must have been a hefty workload for one pilot. Certainly one of the most radical proposals for any program I've seen. Crazy 1960s.

And you've flown one? You've flown anything?

The Model 49 would be easier to fly than a helicopter because despite looking quite odd its just a conventional aircraft.

Technically its not a helicopter because lift is not generated by a rotating wing. However I'm sure the US Army would have called it whatever they wanted to.

The ease of flight depends on several factors besides the flight characteristics of the aircraft. If this particular aircraft was flown with the tactics of an A-10 then it might well have been acceptable for a single pilot aircraft. If it was to operate as a hovering aircraft operating like an attack helicopter it would very likely have been very difficult for one pilot to operate the flight requirements and the weapons and the radios. The US Army has at least twice looked at aircrew workload for rotorcraft and elected to stay with dual pilot. The Russians it seems have elected to forgo the single pilot Ka-50 for the Ka-52 two seat. So if the aircraft had been operated in Vietnam it might well have been a capable aircraft for the Army (assuming the USAF did not object to its mission profile being CAS). However with the end of the Vietnam conflict and the focus on hovering sniper attacks against massed tanks in the Cold War the workload might well have proven very tough for efficient operations. I can tell you from first hand experience that sneaking around between tree lines, knowing where your team mates and the scout helicopter are, talking on four radios, trying to find the enemy while not putting the rotor systems into trees, etc., was challenging for two people in a Cobra.

With the increased automation of the aircraft now being fielded it might well be possible with an integrated flight director, to have single pilot operations as the aircraft would for the most part fly itself, leaving the pilot to communicate and target the weapon systems.

 

[Abraham Gubler]

I can tell you from first hand experience that sneaking around between tree lines, knowing where your team mates and the scout helicopter are, talking on four radios, trying to find the enemy while not putting the rotor systems into trees, etc., was challenging for two people in a Cobra.

Which is why the 49er and other AAFS (“aphis”) contenders had a two crew cockpit. The assumption presented by another poster that it *must* be harder to fly is just not supported. Even in tactical flying the 49er has a range of advantages over a conventional helicopter.

It is much smaller with a footprint 1/5 to 1/6 of a conventional helicopter in flight so it can fit between gaps in the geography, flora and man made structures with much greater ease. Also its outer mould line is not moving. When hovering, ie stationary, the rotor tip of a helicopter is still moving at high subsonic speed so if it hits anything you’re in serious trouble. Because the propeller of the 49er is enclosed when hovering the outer mould line is moving at the same very slow speed as the vehicle. So you can bump into things with a huge margin of collision speed in your favour compared to a helicopter.

Further the cockpit of a hovering 49er is located above the vehicle providing the pilot(s) with line of sight to the ground that includes the vehicle’s edges. In a helicopter the cockpit is suspended under the rotor requiring the pilot(s) to look in two different line of sights to see both the ground and the vehicle edge. To understand the difference imagine trying to park a car where the driver’s position is under the chassis and between the wheels (think of a monster truck to make this easier). Even if the wheels are see through this is much harder than a normal car where you are positioned above the vehicle.

In all regards except one the 49er is easier to fly and manoeuvre tactically in close terrain. The only thing more complex and apparently harder is the moving cockpit. However this would be done automatically connected to an angle of attack meter to keep the cockpit level with the horizon. So it’s a non issue. Unless you lack the imagination and aerospace understanding to try and see how this design would operate and simply reject it as ‘too different’.

 

[Orionblamblam]

The Model 49's cockpit was also much further from the ground than a helicopters is, which could make landings more entertaining. Additionally, ISTR that coleopters like this take a while to tranition back and forther from hover to forward flight, so it might be slower than a chopper in that regard. Compared to a helicopter, its hovering performance would suck; it'd burn fuel faster and would be louder (though the shroud would tend to direct the noise downward-ish). It would have higher disk loading and downwash speed than an equivalent chopper; it'd blow the hell out of the landing field, and I expect desert operations might have to be seriously curtailed. And while the cockipt mechanism could, I'm sure, be made robust and reliable... it can't be 100% reliable. There'd be times when it'd get stuck in one position or another, meaning the pilot would have to land it while lying on his back, or would have to make his way home out of enemy territory while stuck in the vertical hover position. And if something goes wrong with the engines... well, you can't really glide it in like a plane or autorotate it like a chopper; engines go out, you punch out.

It's a nifty design, but it's not without it's negative points when compared to a chopper.

 

[Abraham Gubler]

The Model 49's cockpit was also much further from the ground than a helicopters is, which could make landings more entertaining.

Only if it couldn’t see its own wheels. But it can (or near enough) so this distance is illusory. The S-58 Choctaw/Wessex has its cockpit one level higher than most helicopters and its pilots had no complaints over distance.

Additionally, ISTR that coleopters like this take a while to tranition back and forther from hover to forward flight, so it might be slower than a chopper in that regard. Compared to a helicopter, its hovering performance would suck; it'd burn fuel faster and would be louder (though the shroud would tend to direct the noise downward-ish). It would have higher disk loading and downwash speed than an equivalent chopper; it'd blow the hell out of the landing field, and I expect desert operations might have to be seriously curtailed.

Clearly it wasn’t designed for extended hovering. But the AAFSS specification was not for a Fluda Gap hovering anti tank sniper. Even then the 49er can hover so it can do the mission. Since it can carry a lot more fuel and burn less of it getting from A to B these things should even out. Its not ideal for Action News traffic patrols but its not designed for that. However – as mentioned before – unlike a conventional helicopter the 49er can land in the battlefield in amongst cover and duke it out. It’s got a lot more armour and no vulnerable spinning rotor blades. So rather than hover it can land power down, unload the props and sit in overwatch. Enemy fire gets close and its time to scoot.

As to downwash this is debatable. Unlike a helo it is not sending a dust plume out everywhere but only in the direction of the thrust. So it can keep its nose ahead of the plume. Also the top mounted cockpit keeps the pilots above the plume. Obviously you don’t want to be downwind of it but since even a transport version would carry troops in the ‘kangaroo pouch’ area they should be in front of the plume.

And while the cockipt mechanism could, I'm sure, be made robust and reliable... it can't be 100% reliable. There'd be times when it'd get stuck in one position or another, meaning the pilot would have to land it while lying on his back, or would have to make his way home out of enemy territory while stuck in the vertical hover position.

How many other aircraft have mechanical components that are critical vulnerabilities? All of them… What do you do in your helo when your tail rotor malfunctions – crash. The nose tilt mechanism is one of the simplest items fitted to a aircraft. It bears little weight and has no aerodynamic responsibility. If the hydraulics fail then do doubt there is a manual back up. If that fails you are unserviceable. But since the ledger for the 49er compared to a helicopter is well in the black by not needing a rotor hub, tail rotor, etc this is not a major issue.

And if something goes wrong with the engines... well, you can't really glide it in like a plane or autorotate it like a chopper; engines go out, you punch out.

What makes you think it can’t glide? It has wings… Sure wing loading will be over 100 pounds per square feet so it’s no paraglider but that’s better than nothing. Also it has three engines widely separated inside armoured sponsons. If all that goes – which is an act of god - then at least you can punch out. Lose your engines and half your rotor in an Apache and you’re thinking real hard about how good the crash absorption is on the way down.

 

[Jemiba]

To my opinion, the way the cockpit of the Model 49 was designed could have made the
idea of the Coleopter more acceptable for a lot of people. Especially those civil designs
(BTZ) calling for reclined seating, or swinging around in swivelling seats wouldn't have found
acceptance, except for people, who like merry-go-rounds.
But for the intended application of the Mod.49, I can see this thing and its poor pilot, who
had to double as tank commander and gunner, just as shown below, with the exception, maybe,
if used against an enemy, who is just throwing stones or spears

 

[Abraham Gubler]

I can see this thing and its poor pilot, who had to double as tank commander and gunner,

Why do you people think this is a single seat aircraft? It has side by side seating for two. If you really wanted to you could fit in second row of seats for four.

I think some people really need to read page 1 of the thread or SHOCK HORROR know something about the aircraft before voicing an opinion...

 

[RanulfC]

[quoteTriton wrote:
Anyone have a guess of what the Tri-Service aircraft designation would have been had the Convair Model 49 been built? Would it have been classified as a VTOL airplane or a helicopter? AV-9, AH-56, or a new designation?[/quote]

We shall call it.... Tim... ;D

Ok, it's official now, AG is obviously testing his PR and selling strategy on the forum members. We can probably expect to see the new prototype when?

From what I've seen the major point against the design is in-combat (hover) and long distance ferry fuel use and the coleopters issues during transition from hover to forward flight. (They tended to have a "stall" point they had to power out of as they went from one mode to another. Which could get really 'interesting' close to the ground. Ring/Annular wings don't fly long distances well.) I recently found a patent discussing the issue, (and offering a wing design to get around said issue) by Barnaby Wainfan, and assigned to ACA Industries for a "Free-Wing" variable-incidence wing.
United States Patent 5086993 (aptly named) "Airplane with variable-incidence wing" specifically relating to (though meant for UAVs) ducted rotor craft.

From the Patent summery:
"The craft is for hovering flight, vertical takeoff and landing, and horizontal forward flight. It has a tail-sitting fuselage and a ducted fan mounted to the fuselage aft to provide propulsion in both (a) hovering and vertical flight and (b) horizontal forward flight. At each side is a floating wing, supported from the fuselage for passive rotation (or an actuator-controlled optimized emulation of such rotation) about a spanwise axis, to give lift in forward flight. The fuselage attitude varies between vertical in hovering and vertical flight, and generally horizontal in forward flight. Preferably the fuselage is not articulated; there is just one fan, the sole source of propulsion, rotating about only an axis parallel to the fuselage; and thrust-vectoring control vanes operate aft of the fan. Preferably at each side a small, nonrotating wing segment is fixed to the fuselage, and the floating wing defines--along its trailing portions--a corner notch or slot near the fuselage; forward portions of the fixed wing segment are within this notch. Preferably the spanwise axis is along a surface of the floating wing, and a long hinge supports that wing from the fixed wing segment, within the notch. During vertical and transitional flight characteristically the leading edge of the floating wing is down relative to the fuselage axis."

This would also give the vehicle much better range and loiter time but cause serious problems in hover and manoeuvre around obstacles. Now having said THAT I also thought that the idea of having different wings that could be attached for different missions. Short wings that helped with loiter time and cruise fuel consumption could also have weapons pylons allowing a wider and more diverse range of weapons onboard, while broader and longer wings could be used to add fuel stores and make long range ferry and patrol flights practical.

I'll grant that the coleopter designs had issues but I can't see how they aren't viable designs with their own advantages. In fact I tend to see a production design where there would have been 3 crew members; Pilot, Gunner, and Commander who sat behind and above the other two in a 360 canopy. Given the abilities of the design the "tank-crew" work distribution would seem to offer the most flexability, and crew work-load options.

Pilot to Gunner in AG's picture:
"Aww, shut it you little whiner, you're getting replaced in next upgrade anyway"

Randy

 

[Orionblamblam]

And if something goes wrong with the engines... well, you can't really glide it in like a plane or autorotate it like a chopper; engines go out, you punch out.

What makes you think it can’t glide?

Sigh. Who said anything about it not being able to glide? I said "glide it in."

Look, nobody denies that the B-70 Valkyrie was a perfectly good flier when the engines worked. But the preferred procedure for landing with the landing gear stuck in the "up" position was... point the aircraft towards a shady spot and punch the hell out, because as soon as that intake hit the ground the plane would tumble ass over teakettle, and nobody on board would survive. What exactly about the Model 49 makes you think it would fare any better on an unpowered landing after it swallows a VC crossbow bolt half the size of a telephone pole and loses the internal props? Perhaps you need to re-read the first page of this thread, and pay attention to the actual design of the vehicle.

 

[Colonial-Marine]

No Abraham I haven't flown one, and I rather doubt you have either. Conventional flight is one thing, I am talking about when the aircraft is hovering. I find it hard to believe that there wouldn't be any problems when transitioning back and forth. And when in a hover how is it going to be easier to fly than a helicopter? As much as you enjoy critizing people for not thinking such a radical design is superior to dedicated attack helicopters or fixed wing attack aircraft, there are obviously reasons other than my mindset that has prevented such aircraft from seeing use.

 

[yasotay]

Some other thoughts. It would appear that the aircraft has a rather high center of gravity (I could be wrong) and relatively narrow landing gear profile. This could make landing on slopes (a normal phenomia for field aircraft) more difficult. Another factor is the downwash/outwash which would appear (I could be wrong) to be significantly higher than a standard rotorcraft. Kicking up foreign objects into the vortex flow is not good for any rotorblade. Worse the faster they move. Operating in higher density altitudes might also become more challenging.

All that said, soldiers have a marvelous way of making sh... stuff work. It would certainly have been interesting to see this aircraft downrange.

Ultimatley the biggest problem for the Model 49 was that it was so radical. Military organizations are naturally, conservative. Some more than others. Given a budget and a timeline, conventional tends to be less risky than radical. The only time radical gets an opportunity is through epic failure, or it is not invasive to existing doctrine.

 

[Abraham Gubler]

What exactly about the Model 49 makes you think it would fare any better on an unpowered landing after it swallows a VC crossbow bolt half the size of a telephone pole and loses the internal props?

There are three issues here: can you knock out the 49ers enclosed rotor forcing a loss of powered flight, can you then safely belly land a 49er and why would you do the later if confronted by the former.

While I can imagine shooting a log into the duct of a 49er with a catapult is something the Ewoks could pull off I doubt anyone in our plane of reality could do it. A crossbow bolt down the duct equals wooden sliced salami out the back. But for the sake of argument let’s assume it is possible to knock out the counter rotating prop/rotor head. Possible with a million to one well placed 57mm shot from the rear or down the throat.

Since the 49er is most definitely not a B-70 it would belly land under very different dynamics. Because of the massive pitch control available to the pilot – the elevators have half the surface area of the wing – it could be pulled into a pre landing stall. Annular wings don’t have good stalling response but you can use this to reduce the landing speed to manageable levels. Since the centre of gravity is going to be behind the lip of the shroud there is no reason to assume an automatic pitch forward unless you run into an obstacle. Which would ruin your day belly landing even the most fish shaped aircraft. Even if you do pitch forward unto the cockpit it is both a heavily armoured steel shell and has a stress release function thanks to the articulating capsule. So in any such crash the cockpit is not going to crumple and is going to break free of the fuselage keeping the crew free of the tumbling body.

Which of course raises the final question why would anyone glide in a complete thrust failure 49er? It isn’t a helicopter. If it losses its engines or rotors the crew are not strapped into the fuselage with no where to go but straight down. They can eject or in this case eject the crew capsule. This is like saying to the pilot of an F-16 they can’t use their ejection seat if they lose their engine and they have to glide it in… Hell no, I’m punching out.

So who’s going to Page 1 of this thread or Page 3 of Aerospace Projects Review Volume 2 Number 2 to read more?

 

[Abraham Gubler]

Conventional flight is one thing, I am talking about when the aircraft is hovering.

Were you? Thanks for letting us know that… You could have been talking about anything to yourself but this is a forum where people talk to each other via clearly communicated words and if you aren’t going to do that just make bold declerations or opinion expecting us to read your mind to know your context then your expectations are a bit misplaced.

But again the question remains what makes you think it would be hard to hover? Have you consulted Skeets Coleman and Bill Chana on this issue? Assessed their opinions on the matter? Understand the issues of directional thrust hovering compared to rotating wing hovering?

I find it hard to believe that there wouldn't be any problems when transitioning back and forth. And when in a hover how is it going to be easier to fly than a helicopter?

You can believe anything when you don’t know anything about it but there have been plenty tail sitting aircraft which have proven the capacity to transition from vertical to horizontal flight without much aerodynamic problems. The main problem is pilot orientation which of course is solved in the 49er by the articulating cockpit.

As to what makes it easier to hover is that you control your attitude via conventional yaw, pitch and roll controls. With Bill Chana’s throttle vernier control and vertical/horizontal switch between roll and yaw controls hovering is easy peasy. As easy as a helicopter but with all the configuration advantages like pilot view and spatial relationship to the rest of the vehicle.

As much as you enjoy critizing people for not thinking such a radical design is superior to dedicated attack helicopters or fixed wing attack aircraft,

There’s your problem there. You seem to think this is some kind of personal contest. It isn’t. So now that you know that can you stop trying to compete as if it is?

there are obviously reasons other than my mindset that has prevented such aircraft from seeing use.

No your mindset is the reason. Same mindset and same reason* as to why we don’t have humans living on Mars, global supply of cheap clean energy, dragged the third world through the enlightenment, dragged everyone in the first world through the enlightenment and basically all the good things humans could do but haven’t.

* Disclaimer: this mindset I am referring to is not a conspiracy theory or such nonsense as interpreted by another poster but the rejection of the different. See my signature for further on this issue.

 

[Abraham Gubler]

Some other thoughts. It would appear that the aircraft has a rather high center of gravity (I could be wrong) and relatively narrow landing gear profile. This could make landing on slopes (a normal phenomia for field aircraft) more difficult.

This is a good point. The four wheels are separated by a diameter of about 23 feet and the centre of gravity – going by engine location – is probably about nine feet high. So that’s not so bad. But the 49er in the vertical configuration is likely to be forward loaded because of position of the articulated armoured cockpit capsule and the heavy weapons pack. So if you land on a slope you keep it facing uphill so the forward loading pulls the aircraft into the slope and away from tipping over. But even if it was to tip over it shouldn’t cause any major damage. Because of the very high structural strength of the armoured annular wing and enclosure of all moving parts. So you can right it with a crane and then take off again… try doing that in an a Apache…

Another factor is the downwash/outwash which would appear (I could be wrong) to be significantly higher than a standard rotorcraft. Kicking up foreign objects into the vortex flow is not good for any rotorblade. Worse the faster they move. Operating in higher density altitudes might also become more challenging.

Because of the duct and the high speed of the downwash it would likely act more like a jet of air than a conventional rotors vortex. So as long as you keep a bit of forward movement as you hover into land all that bad stuff in the downwash is going to be behind you.

 

[Orionblamblam]

While I can imagine shooting a log into the duct of a 49er with a catapult is something the Ewoks could pull off I doubt anyone in our plane of reality could do it.

Sadly for Air Cav, the VC managed just that. My father's platoon was in a firefight where one of the Hueys was brought down by a giant crossbow... hit the engine, brought the chopper right down. My father examined the bolt... something like 3 to 4 inches in diameter, 10 or so feet long. One of those puppies hit's your bird, you've got problems.

A crossbow bolt down the duct equals wooden sliced salami out the back.

Only if it's an itty-bitty bolt. Rotor and props tend to dislike hitting large, hard things.

Possible with a million to one well placed 57mm shot from the rear or down the throat.

Or with branches, since this thing is going to be hovering in forests and such.

Or if it swallows a big Canadian goose.

Since the 49er is most definitely not a B-70 it would belly land under very different dynamics.

Yeah. *Even* *worse* dynamics. There is only one way to land this thing: on its ass, vertically.