McDonnell-Douglas F-15 Avionics, AN/APG-63/70 radar

[overscan (PaulMM)]

Thread to discuss F-15 avionics.

I am particularly keen to learn more about the APG-63 radar.

 

[Dilbert]

I did some research on F-15 radars fairly recently. What would you like to know?

There's some pretty good technical information in the Peter E. Davies and Tony Thornborough book, "McDonnell Douglas F-15 Eagle". Steve Davies (no relation) also provides a good description in his "Boeing F-15E Strike Eagle" book, but it pertains to the newer APG-70 version.

You can also check http://www.f15sim.com , click the "Misc" button and look for the left console image for the F-15C (F-15E images also available). It shows different radar control panels according to the version - APG-63, APG-70 or APG-63(v)1. Compare as you dare!

 

[overscan (PaulMM)]

I'm trying to get hold of the Davies/Thornborough book, but I'm very interested in the APG-63 radar. Specifically I've heard in various places

The initial (pre-PSP) APG-63 doesn't have a TWS mode

The capabilities of the initial APG-63 fall somewhat short of the 100nm+ fighter detection range sometimes claimed (which makes sense to me, given how much cheaper than the F-14 the F-15 was)

 

[Dilbert]

TWS "as we know it" wasn't introduced until APG-70, AFAIK. What the PSP introduced was something called Raid Assessment Mode (RAM). It was an interleaved mode that would alternate each normal scan of the search volume with a finer "spotlight" scan of up to four priority targets. RAM was unpopular with pilots compared to TWS and has now been removed, as I believe has DTT (dual target track), apparently because these multi-target modes required the targets to stay within a smaller search volume in order to work. The simple, no-nonsense all-or-nothing options of either TWS or STT are apparently preferred.

I also heard somewhere that AWG-9 power was "9 kW", APG-63 "5 kW"

Sources
- Peter E. Davies and Tony Thornborough, "McDonnell Douglas F-15 Eagle", 2001
- Forum discussions with crew members at http://www.f-15estrikeeagle.com

 

[overscan (PaulMM)]

I've got a lot of information from various sources which I am compiling into a PDF document right now.

I'll post it here for you to check over.

Paul.

 

[Pit]

This is an information about the upgrades made to F-15C MSIP II and F-15E Strike Eagle's radar systems, and came from Jane's Radar and EW Systems 2001-2002.

The APG-70 signal processor employs modular parallel processing (controlled by a MIL-STD-1750A central processor unit) and operates at speeds in excess of 30 million complex operations/s (potentially upgradable to 40 Mops). The sensor's radar data processor performs general purpose computations and has been upgraded to 1,024 k of memory. This is over 10 times greater than that available in the APG-63 and the unit operates at between four and five times faster. Approximately 220 k is devoted to air-to-air modes, 110 k to air-to-ground, 200 k to the built-in test feature and 64 k to scratchpad memory. The remainder is spare memory that is available for future enhancements.

Now, APG-70's PSP is what I think is based around RISC MIPS R3001 (or 4000) chips (multiple processors), with software running on ADA high level language isn't?.

Now the bold text, it talks about the IBM CP-1075 main computer?, or there is an specialized Radar Data Processor on F-15C?...I know since F-15A, Eagle uses an IBM designed computer called CP-1075, this was actualized till CP-1075C model on F-15E Strike Eagle from 1992...

Is this computer related to radar data processor tasks (sort of Ts100 series computers on Soviet A/C) or is a mission computer or just a mix of both of them?.

 

[overscan (PaulMM)]

Am I correct in saying MSIP II did NOT install APG-70 on all F-15C as intended?

In which case, did did F-15C still have APG-63 PSP (1979) until APG-63V1?

If so, were TWS and NCTR added to the APG-63 PSP?

 

[overscan (PaulMM)]

Another question-

What is the purpose of the ALQ-128 EWWS?

 

[Dilbert]

AFAIK there might still be some F-15C flying with APG-63PSP today. The acquisition process was a real mess.

Soon after APG-70 was developed for F-15C, the F-15E came into being and received priority. Unfortunately, the APG-70 radar components were quickly no longer manufactured, because of rapidly progressing technology, and this created a maintenance nightmare. ALL APG-70 were cannibalized from the F-15C fleet, to serve in F-15Es. The situation was, ironically, less critical for the far older APG-63PSP, because the large numbers of F-15As being decommissioned freed up the older radars to be used as spares.

AFAIK only 161 APG-63(v)1 and 18 APG-63(v)2 were delivered to F-15C units. So, all F-15Cs beyond these 179 aircraft should be using APG-63PSP even today.

What is the purpose of the ALQ-128 EWWS?

It's associated with the hush-hush "enemy IFF interrogator" function that made its debut as Combat Tree in Vietnam. I'm not sure if it's a transmitter, receiver, or both. It's the pod on the left tail fin, that is absent from Israeli and other export Eagles.

Sources:
- P. Davies and T. Thornborough, "McDonnel Douglas F-15 Eagle"

 

[overscan (PaulMM)]

Here are the radar panels from the F-15 from the F-15 Flight Manual

 

[Pit]

APG-63 looks pretty basic:

LRS: Long Range Search, I guess it could well be an interleaved HPRF and MPRF RWS radar mode.

VS: Velocity Search, HPRF without FM.

SRS: Short Range Search, like "ACM" HUD mode on APG-66?...there is no vertical scan short range radar modes?

PULSE: Pulse Radar mode.

BCN: Beacon mode for finding Tanker.

Then there are the three air to ground radar modes, Doppler (DBS?), RNG (Range Ranging?) and MAP (Real Beam Map)...

There are four tracking options, OFF (no tracking) MANUAL (manual tracking, how did the pilot do it?), TRK (automatic tracking), SNIFF (jamming pulse tracking) and FLOOD (for short range AIM-7E2 and AIM-7F use)...

AZ SCAN, Azimut selection, 20 (+-20°), 40 (+-40°), 60 (+-60°)...are all options available for all modes? I guess.

RADAR EL SCAN (1, 2, 4, 6, 8) I guess that controls radar bars options for ALL radar modes.

RANGE 10, 20, 40, 80, 160 (display range presentation, till 160nm)

FRAME STORE PUSH TO ERASE (0, 1, 2, 3, 0, 1, 2, 3)...no IDEA...maybe a sort of "memory of traces", sort of blip appears at here then at here, and then here (*---*---*) and this options allow you to see those radar blips sucessions?...any idea?

I guess this is first APG-63 (NO PSP), but with APG-63PSP (with RAM mode sort of TWS but only against four targets), how did the panel changes?...

Wich radar modes were introduced with PSP?, RAM, Sort (?)...

Thanks for anwers!

It didn't look that advanced over N-001 after all

 

[overscan (PaulMM)]

Marcos, IOC of the F-15 with APG-63 was more that 10 years before the Su-27. As Andrei Fomin says in Flanker Story, the N001 largely matched the original APG-63, but the US had already upgraded to PSP from 1979 and from 1985 APG-70 was coming along nicely.

 

[Dilbert]

It didn't look that advanced over N-001 after all

That's what I thought at first.

In fact, the panel controls are misleading - note that the new control panels seem to have fewer controls than the old one!
Unlike MiG-29/Su-27, in the F-15 the most numerous radar controls (including all RAM/TWS controls) are on the HOTAS.

If I remember correctly, LRS includes both HPRF and MPRF modes, selected by HOTAS. SRS is the "vertical scan" mode.

 

[overscan (PaulMM)]

The APG-63 is an aging, complex,
electronic subsystem that is critical to the operational effectiveness of the F-15 C/Ds
which are still the front line air superiority fighter of the U.S. Air Force (AF). The subject
of this study is the version of the APG-63 with the programmable signal processor that
was installed in all but 43 of the 470 F-15 C/Ds delivered to the AF.

Hardware design Mean Time Between Failures (MTBF) was
about 75-80 operating hours, with a field experienced hardware MTBF of 25-30 hours.
However, the Mean Time Between Maintenance Actions (MTBMA) was only 12-14
operating hours. Can-Not-Duplicate (CND) rates were 47% and Bench-Check-
Serviceable (BCS) rates were 39%.

Moreover, the APG-63 suffered from memory and throughput constraints. Its
current Operational Flight Programs (OFPs) utilized over 98% of its 98K of memory and
its throughput was not adequate for some desired operating modes thereby limiting future
upgrades to its software.

APG-70 logistics performance problems were attributed to upstream processes. Ninety
two percent of the problems were attributed to hardware design, software design,
manufacturing design and variability, and diagnostics. The Eagle Century study found
that the development processes used during the APG-63 and APG-70 developments
exhibited the following characteristics that contributed to the problems identified.
• Too much emphasis on in-flight performance.
• Incorrect tolerances and margins
• Producibility not adequately considered in design
• Support not adequately considered in design.
• Life cycle costs not adequately considered in design.
• Real stresses induced by the operating environment not considered in design.
• Failure modes and durability not addressed in design.

The APG-63 upgrade was not under pressure to use risky technologies. The basic
in-flight performance of the APG-63 still met AF requirements so the performance
requirement was set at the same performance as the APG-70. Electronics technology has
advanced greatly in the time since the APG-63 and APG-70 were designed. Therefore,
adequate, low risk technology was available to meet program requirements.

http://dsc.aticorp.org/documents/chap2_apg-63.pdf

 

[Pit]

Marcos, IOC of the F-15 with APG-63 was more that 10 years before the Su-27. As Andrei Fomin says in Flanker Story, the N001 largely matched the original APG-63, but the US had already upgraded to PSP from 1979 and from 1985 APG-70 was coming along nicely.

Indeed you're correct.

But I do consider the APG-63 the "more flexible" system after all.

OK, N-001 works in an eternal TWS mode (that's cool for SA building along Tactical Display Mode options and K-DlA datalink), but it lacks the flexibility of basic APG-63 after all, the bar/range-display/azimuth presettings options that are fine for helping the pilot to get the best of the radar in terms of MMI (man-machine interface)...plus the HOTAS arrengement!.

But, How could we consider the performance (on raw terms) of AN/APG-63 vs N-001 in LRS vs SnP modes?...I guess, those maximum performance capabilities of AN/APG-63 (100nm for fighter detection/tracking) looks for non FM HPRF mode (VS) and I do think that without VERY good GCI/ACI control for telling you "where to see and what Vc to expect"...no range/time-acquisition advantage are gained over this mode...

SNIFF tracking option looks interesting...is same functionality as AP/APKh options on N-001/N-019? (Track On Jam over Noise jamming, Kinematic Range Method)?...I would love how to get a manual trackin solution on AN/APG-63 and family...one thing is to be on a ground radar (radar operator is not flying so he could concentrate on blips and so), but while flying?...looks as a difficult thing to do!.

APG-63 basic is reputed to use Kalman filtering for tracking solutions...would love to understand this concept a little more and know if N-001 and similars used it...ups this is not soviet topic

Dilbert I have some questions if you don't mind!...

Apart of RAM mode what other mode is introduced on AN/APG-63PSP?...DTT?, is DTT similar to RWS-double SAM on APG-66(V)2 on F-16AM MLU?.

Did AN/APG-63PSP received the new PSP and radar data computer evolved from MSIP-II even if not the whole radar as such?...or were all the gismos reserved to those 33 F-15C that received the AN/APG-70?.

Did you know what is Spot-light and Sort modes?.

Thanks a bunch guys!

 

[overscan (PaulMM)]

APG-70 (image from US Air Force)

 

[overscan (PaulMM)]

F15C032 - NON-COOPERATIVE TARGET RECOGNITION (NCTR) UPDATES - MAX
(OPERATIONAL CAPABILITY)
DESCRIPTION: A software change to the APG-63(V)1 and APG-70 radar to identify approximately 14 target types. Includes improvements to NCTR algorithms to reduce incorrect identification and improve performance. This program requires changes to the radar Operational Flight Programs (OFPs) and the Central Computer OFP in F-15 Suite 6. Common with F-15E.
JUSTIFICATION: Failure to update the aircraft NCTR capability with these 14 target types will limit the pilot/aircrew to visual target identification, decreased survivability, and restricted weapon employment.
PROGRAM ELEMENT: PE 27130F.
ISSUES: NCTR upgrade MAX will be incorporated in Suite 6 OFP software. 164 F-15C/D aircraft will be retrofitted with APG-63(v)1 radars and receive the OFP update.
REFERENCES:
MNS Number & Title: Tactical Air Forces (TAF) Required Operational Capability (ROC) for Advanced Aerial Combat (F-X), (ACC ROC 9-86)
ORD Number & Title:
1067 Number & Title: Development Plan Date & Title:
Current CINC IPL: YES
ACC PEM Name: Maj Kent, DRAO, 4-3861 PEM Backup Name: Maj Johnson, DRAO, 4-3861

 

[overscan (PaulMM)]

F15C031 - COMBAT IDENTIFICATION
DESCRIPTION: A software change for the APG-63(V)1 to positively identify potential targets using cooperative and non-cooperative techniques. Technology insertion of Wright Labs developed algorithms. This change requires APG-63(V)1 Radar, Operational Flight Program Suite 4M (for partial capability), and OFP 5M (for full capability).
JUSTIFICATION: Corrects an existing shortfall in Air Force employment of high tech, long range weapons (i.e. AMRAAM) due to limited capability to positively ID targets at or beyond full weapon employment range. The software change increases the existing database to include threat data not included during initial development.
PROGRAM ELEMENT: PE 27130F
ISSUES: CID upgrade is incorporated in Suite 4 and Suite 5 OFP software. 164 F-15C/D aircraft will be retrofitted with APG-63(v)1 radars and receive the OFP updates.

 

[overscan (PaulMM)]

This is a good start Andrew. Here are some APG-70 specific features I’d love to see someday:

Master mode selections of:
A/A Mode
A/G Mode
ADI Mode
VI Mode. Once a target is locked, the ASE circle and dot will provide steering data to bring the aircraft directly behind the target

A/A Attack Mode Selection, weapon select. This is a three position select switch on the throttle that enables GUN, SRM, or MRM

A functional mater arm

Elevation bar scan selection of 1, 2, 4, 6, and 8

Frame store selections of 0, 1, 2, and 3

All standard radar search modes including:
1- MED: MPRF for search and TWS for 10, 20, 40, and 80 range scales.

2- INLV: MPRF and HPRF for 20, 40, and 80 range scales. Alternating INLV or HPRF scans at 160 and MPRF only at 10.

3- HI: HPRF at all range scales and search and TWS modes.

4- VCTR: Velocity search between 80 and 2,400 kts relative

5- RGH: Uses an intermediate PRF between MPRF and HPRF that gives good all-aspect acq. The 10 -20 nm scale uses a short pulse wave form to provide better break out sensitivity. Not to be uused below 6,000 AGL

Auto Acq. Modes:
1- Boresight
2- Long Range Boresight
3- Supersearch
4- Vertical Scan
5- Gun Scan

All TWS Modes:
1- NDTWS
2- DTWS
3- HDTWS
4- NDHDTWS

NCTR interrogate (coolie switch inboard)

Additional MPCD functionality:
1- Combat jettison
2- JTIDS display (SIT), functions including:
Auto-range (tied to VSD range)
PDT lock/launch line
Altitude and radar coverage lines
Reference lines and area symbols
Waypoint and route symbols
Ownship weapon inventory
Declutter
Friendlies
Data
Strength/type
H SAM
Ship
Radar coverage
Routes
Lines
4- A/A and A/G PACS select (FYI. PACS is one portion of the MPCD functionality)
5- MRM target size select
6- Flight member ID input (for deconflict)
7- Color indications for weapon status
Green = ready
Amber = failed / hung
White = stand by
8- COOL switch set to on when master arm activated
9- A/G weapon video display
10- AIM-9 self-track toggle

Cycle through TWS targets in priority list by range to be PDT when tapped less than one second. When held more than one second, nearest track is set to PDT (coolie up)

TWS undesignated target (aft on boat switch)

Weapon reject cycle option. When selecting MRM (AIM-120 / AIM-7), missile reject is used to cycle between types

When TDC is pressed for less than one second, radar antenna should be slaved to TDC azimuth position. Hold TDC more than one second command SORT mode that includes 30-degree azimuth that is heading stabilized.

On HUD, cue for AIM-120 selected is “A(number of type remaining)C”, AIM-7 is “M(number of type remaining)M”, and AIM-9M is “S(number of type remaining)M”

If missile type onboard that is not in priority is also between Rmin and Rtr, that weapon cue (S4M for example) will flash next to the current weapon in priority

With MRM selected, the selected target size (from the PACS) should be displayed on the HUD unless set to Normal.

When an MRM is launched, the current present position and time of day are displayed on the HUD

Track memory (MEM) mode should have the TD box flash on the HUD when the radar has lost lock but is still trying to reacquire

SNIFF special mode indicators should be on HUD when appropriate

JAM, HOJ, AOJ should be moved to the top of the lower right data block on the HUD

If more than one missile is in air at the same time, the TOF for the minimum and maximum times are displayed on the HUD.

An Enhanced Identification (EID) box cue should flash in the TD box when the target has been interrogated to be a friendly

Along the bottom of the VSD, the magnetic bearing and range to bull’s eye is displayed when in search and TWS modes. When in STT, the magnetic bearning and range between bulls and target is displayed.

Along the right outer side of the VSD, the aircraft’s present lat/long position is displayed.

In addition to the current GDS gunsight, provide LCOS version as well

Include the Ropt cue on the VSD

TWS scan should center on PDT

TWS modes should be inhibited when in guns mode

MAR bar on the missile fly-out line

Hot and Cold hit icons when in a LRS mode

Add Expanded Azimuth Display. This is enabled when in STT and the target is more than 45-degrees off in azimuth. When this happens, the azimuth is increased to +/-75 degrees and the outter grid line represents break-lock point.

SNIFF mode in general is a receive only (standby) mode used to detect jamming of the radar channels or to provide a minimum radar radiation time to prevent detection. Targets that are jamming the radar are received as the antenna sweeps past their position.

DTWS = Designated TWS (normally entered from STT, HOJ, or NDTWS / HDTWS)

NDTWS = Non-Designated TWS (entered by TDC designating VSD or using undesignated boat switch function).

HDTWS = High Data rate TWS (faster track updates). Entered like DTWS but can cycle between DTWS and HDTWS with auto-acq switch forward

NDHDTWS = Non-Designated, High Data rate TWS. Entered like NDTWS, but can cycle between the two with the forward auto-acq switch.

The MRM target size selection influences the AIM-7 Dynamic Seeker Range (DSR) and the AIM-120 Missile Active Range (MAR) calculations.

Regarding flight member ID, this ID is important in the real world to prevent missile-to-missile mutual interference (MI) between AIM-120s launched among aircraft in the same flight.

Regarding item 7: at least as far as the APG-70 goes, the Sort Mode simply places it in a 30-degree azimuth scam that is heading stabalized. There does not appear to be any "zoom" function.

There is the RAM function, but I hear this is being, or has already, been phases out in current tapes (it was a joke).

Postings by Wags in this thread; http://forum.lockon.ru/showthread.php?t=5658&page=1

 

[Pit]

Just Awesome!

Thanks a lot fur putting that here!...

 

[Dilbert]

Apart of RAM mode what other mode is introduced on AN/APG-63PSP?...DTT?, is DTT similar to RWS-double SAM on APG-66(V)2 on F-16AM MLU?.

From the same source, only RAM mode was added with PSP, but the Pulse mode was changed from LPRF to MPRF at the same time.

Did AN/APG-63PSP received the new PSP and radar data computer evolved from MSIP-II even if not the whole radar as such?...or were all the gismos reserved to those 33 F-15C that received the AN/APG-70?.

Hmm, interesting, I thought MSIP II WAS the APG-70. But according to this,

http://www.af.mil/factsheets/factsheet.asp?fsID=101

...it seems that only the "final 43" to go through MSIP II received the APG-70, how odd.

Did you know what is Spot-light and Sort modes?.

Spotlight is like a "mini-STT" that is used on up to four targets in RAM mode.
Sort is apparently just normal TWS mode with the scan pattern narrowed to +-30 degrees, and the pattern centered on the radar cursor. Nothing very special about it except the name, AFAIK.

Sources:
- http://www.f-15estrikeeagle.com

 

[Pit]

Spotlight is like a "mini-STT" that is used on up to four targets in RAM mode.
Sort is apparently just normal TWS mode with the scan pattern narrowed to +-30 degrees, and the pattern centered on the radar cursor. Nothing very special about it except the name, AFAIK.

Interesting, many thanks for the answers, so RAM is a "sort of" TWS that works on a time-shared STT pattern...how do you select the targets to be "tracked" in RAM?, automatic priorization like on SnP on N-001?, is the time-shared STT vulnerable to lock-on detection or should be so short in time-to-time of the jumping of the STT between the targets that no lock on could be aparent?.

 

[Vadifon]

whether somobody knows the angle of "Bank (roll) stabilization" for APG-63 (early) and APG-70?
can APG-63 safe the possibility of tracking target (STT mode) if aircraft roll is more than 1xx°?

 

[Pit]

whether somobody knows the angle of "Bank (roll) stabilization" for APG-63 (early) and APG-70?
can APG-63 safe the possibility of tracking target (STT mode) if aircraft roll is more than 1xx°?

AFAIK, stabilization in pitch and bank is donde electronically in both APG-63 and 66, so there is no limit (antena rotation) like on N-001/N-019.

 

[Vadifon]

AFAIK, stabilization in pitch and bank is donde electronically in both APG-63 and 66, so there is no limit (antena rotation) like on N-001/N-019.

For APG-66 it's correct, but APG-63(except for v2) & APG-70 have roll-hyrostabilazed.

 

[Vadifon]

IMHO при анализе возможностей Н-001/19 я пришел к выводу что при выполнении вращения по крену в 360 градусов реальное сопровождение цели будет сорвано (хотя экстраполируя параметры цели БЦВМ сохраняет математическое сопровождение в течении нескольких секунд).
Упоминаются ли ограничения у APG-63 при режиме STT всвязи с гиростабилизированной антенной по крену ?
У меня есть данные (APG-63 ранний), что угловая скорость сопровождения цели в режиме STT 20 градусов в секунду - это правильно?

[Machine Translation by Overscan]

IMHO with the analysis of possibilities N -001/19 I came to conclusion that with accomplishing of rotation along the bank into 360 degrees real target tracking will be lost (although extrapolating the parameters of target BTsVM [computer] preserves the mathematical accompaniment in the course of several seconds).
Are mentioned limitations in APG-63 with the mode STT of [vsvjazi] with the gyrostabilized antenna along the bank?
I have data (APG-63 early), that the angular accompanying velocity of target in the mode STT of 20 degrees per second - this is correct?

 

[mrdetonator]

IMHO при анализе возможностей Н-001/19 я пришел к выводу что при выполнении вращения по крену в 360 градусов реальное сопровождение цели будет сорвано (хотя экстраполируя параметры цели БЦВМ сохраняет математическое сопровождение в течении нескольких секунд).

If I understood you correctly, the N-019 will loose radar "lock" if a pilot rolls more than 360deg. How much time(in seconds) the BTsVM computer will maintain the target "lock-on" when rolling more than 360deg? I know the N-019 is gyro-stabilized in the roll +/- 120degree in search(scan) mode, it is written in the manual. Does this limitation apply to the STT mode as well?

 

[overscan (PaulMM)]

In search mode, the scan pattern is a horizontal pie slice. Hence, when banking, the N019 is stabilised in order to keep the scan pattern aligned with the horizon. If you are in STT mode, the radar beam is permanently pointing directly at the target. So why would you need to stabilise the radar in bank?

 

[Vadifon]

N019 is always stabilased in banking i.e. search mode and track mode. I think it concerns APG-63 in the BVR

 

[Vadifon]

If you are in STT mode, the radar beam is permanently pointing directly at the target. So why would you need to stabilise the radar in bank?

Это заблуждение - Н-001/19 всегда стабилизирован (смотри файл). Продолжать дискуссию по стабилизации APG-63 при помощи машинного перевода сложно. Думаю нужна помощь Andrew .

 

[overscan (PaulMM)]

The F-15C's (APG-63) antenna achieved roll stabilization using azimuth (side-to-side) and tilt (up-down) as you described. One of the maintenance tests for the antenna verified that it could physically scan smoothly from top-left to bottom-right.

There were roll limits to the stabilization.

Jim (F-15 Attack Control Systems back in the day (A-Shop))

frugalsworld.com

This domain may be for sale!

forums.frugalsworld.com

 

[Vadifon]

and ???
some questions^

 

[mrdetonator]

IMHO при анализе возможностей Н-001/19 я пришел к выводу что при выполнении вращения по крену в 360 градусов реальное сопровождение цели будет сорвано (хотя экстраполируя параметры цели БЦВМ сохраняет математическое сопровождение в течении нескольких секунд).

I`ve verified 100% that the N-019 will not loose radar lock, while simultaneously rolling the Mig-29 more than 720degree!!!. Not sure if it does fit your theory?

 

[Vadifon]

It is possible with computer extrapolation (but it is limited on time)
я говорю о способности антенн следовать целям при крене (without computer extrapolation), а не о том что пилот потеряет цель

 

[mrdetonator]

It is possible with computer extrapolation (but it is limited on time)

What "limited time" are you talking about, please let me know so we can check it out. What if the radar "lock" holds more than 10second while simultaneously rolling the aircraft, does this still prove the target has been extrapolated in the computer?

я говорю о способности антенн следовать целям при крене (without computer extrapolation), а не о том что пилот потеряет цель

Are you sure the N-019 is gyro-stabillized in tracking mode as well as in the search mode, how you came to that conclusion?
thanks

 

[Dilbert]

Hi guys,

As overscan noted, this is a fairly old question from other forums.

mrdetonator, if you look at the animation Vadifon provided in Reply #29 on page #2 of this discussion, you can see that the small circle symbol indicates the angular direction that the locked radar antenna is looking to the target, even as the aircraft symbol enters a bank with respect to the drawn horizon. This creates some ambiguity - is this symbol drawn with respect to
(a) the horizon line, drawn in the HUD, which is now banked X degrees with respect to the real horizon,
(b) the aircraft symbol, drawn in the HUD, which is now banked 2X degrees with respect to the real horizon,
(c) both (a) and (b) above (are the same thing), or
(d) the real horizon, outside the HUD?

We can eliminate (d) because the symbol does not seem responsive to the aircraft's banking - if it was (d) then the symbols would move right-to-left while the aircraft is banking.

The answer seems to be (c), and some people are convinced that this is evidence, that the radar antenna IS gyro-stabilized with respect to the horizon, even when locked on a target.

I'm not yet convinced, but I'm also not sure that I understood the logic correctly, so I don't argue. You can make your own analysis and judgement from this evidence.

As for "limited time" - the radar computer has some memory, so that if it loses lock for any reason, it can extrapolate the position of the target until it (hopefully) re-acquires lock after a few seconds. So, if I understand correctly, Vadifon thinks that after a fast enough 720-degree roll, the antenna will be back in its correct orientation and be able to "re-lock" the target without the display ever indicating that the lock was lost.

Of course, by this logic, I think that a MiG-29 banked at 140 degrees should then have its +-120 degrees gyrostabilized antenna able to rotate 360 degrees in the other direction to re-acquire the target even in this banked position, so I don't understand in which situation, if any, lock would be expected to be lost, if not in the 720-degree example you provided. Thanks for your information!

 

[Dilbert]

and ???
some questions^

In the APG-63, the guard horn antenna is attached to the slotted array. It scans in every direction together with the main antenna, unlike the guard horn in Russian radars that is fixed. So for this reason, I don't think that bank in a western fighter has any significant effect on guard horn operation.

 

[Vadifon]

We can eliminate (d) because the symbol does not seem responsive to the aircraft's banking - if it was (d) then the symbols would move right-to-left while the aircraft is banking.

You got me correctly. But re. Reply #29 РНП.gif. Please notice this picture was restored from the real target tracking of N-019.

The answer seems to be (c), and some people are convinced that this is evidence, that the radar antenna IS gyro-stabilized with respect to the horizon, even when locked on a target.

Please notice this picture was restored from the REAL target tracking of N-019.

As for "limited time" - the radar computer has some memory, so that if it loses lock for any reason, it can extrapolate the position of the target until it (hopefully) re-acquires lock after a few seconds. So, if I understand correctly, Vadifon thinks that after a fast enough 720-degree roll, the antenna will be back in its correct orientation and be able to "re-lock" the target without the display ever indicating that the lock was lost.

You got me correctly. You can even see it at the picture mentioned above РНП.gif where you can see a computer extrapolation (in azimuth). It starts from aspect target R120

Of course, by this logic, I think that a MiG-29 banked at 140 degrees should then have its +-120 degrees gyrostabilized antenna able to rotate 360 degrees in the other direction to re-acquire the target even in this banked position, so I don't understand in which situation, if any, lock would be expected to be lost, if not in the 720-degree example you provided. Thanks for your information!

Lock would be expected to be lost at 120-240 bank degrees (+taking into account the time of correct orientation)

 

[Vadifon]

In the APG-63, the guard horn antenna is attached to the slotted array. It scans in every direction together with the main antenna, unlike the guard horn in Russian radars that is fixed. So for this reason, I don't think that bank in a western fighter has any significant effect on guard horn operation.

Andrew, what would you think of the following: the guard horn and antenna of Russian aircrafts are stabilized with bank. The difference from APG-63 is in pitch direction.

PS. all previous questions are needed to be answered.

Andrew, thanks a lot for your interpretation. All English text was translated by Sobina. I hope there are not many mistakes.

 

[Dilbert]

The answer seems to be (c), and some people are convinced that this is evidence, that the radar antenna IS gyro-stabilized with respect to the horizon, even when locked on a target.

Please notice this picture was restored from the REAL target tracking of N-019.

It's understood. I don't contradict the authenticity of the diagram. Rather, I have difficulty to make the conclusion that this animation demonstrates antenna roll-stabilization during a lock. I think that the animation could still appear the same, regardless whether the antenna is roll-stabilized or not. The antenna symbol in the HUD shows only its angular aiming direction, and the roll angle of the aircraft - not the antenna's own roll angle, independent of the aircraft roll angle.

Of course, by this logic, I think that a MiG-29 banked at 140 degrees should then have its +-120 degrees gyrostabilized antenna able to rotate 360 degrees in the other direction to re-acquire the target even in this banked position, so I don't understand in which situation, if any, lock would be expected to be lost, if not in the 720-degree example you provided. Thanks for your information!

Lock would be expected to be lost at 120-240 bank degrees (+taking into account the time of correct orientation)

You're right, my mistake - so now mrdetonator should check to see if MiG-29 can hold lock on targets, while flying upside-down for more than 12 seconds?

There's another problem when flying inverted for extended time - I think that the accumulator fuel tank in modern jets only works upside-down for some seconds, no?

Andrew, what would you think of the following: the guard horn and antenna of Russian aircrafts are stabilized with bank. The difference from APG-63 is in pitch direction.

There are some other differences. If I understand correctly, in Russian aircraft the guard horn significantly decreases the maximum detection range, so there is a switch in the cockpit to use or not use it, as necessary. I never heard of such a switch in the Western cockpit.

English is good, hello to Sobina, but - call me "Dilbert"