Autopilots on modern fighters

[stilton]

Curious about the capabilities of autopilots on modern fighters, I would imagine in the past they have been fairly basic but what about Typhoon / Rafale / F22 etc ?


Can they, for example fly an entire route with different waypoints, level off at a preselected altitude, fly a 'Vnav' descent to a predetermined fix, or an ILS approach, even an autoland ?


I believe the F18 can fly an automatic approach to a carrier ?


Any fighters with autothrottle(s) ?

[Dash8driver1312]

A single F/A-18 had been used by Boeing in the development of autoland software. It never made a full landing under autopilot but demonstrated the technology for use with a drone which has made successful arrested landings.

Typhoon includes a system in case of pilot incapacitation that levels the wings and puts the aircraft into a slight climb. I do not know what logic it uses to establish G-induced Loss Of Consciousness has happened but that's how the system is advertised.

[Rhino power]

The USN were messing around with an auto-land system via datalink back in the early to mid 60s, using a numer of F-4G Phantoms, i think it was also linked in with the aircraft's existing autopilot...

-RP

[Timelord]

Can't speak for "modern fighters" but the Tornado GR1/4 has a pretty good AP because it was designed to fly an entire route at low level, on Terrain Following Radar with the AP engaged. The autothrottle can maintain a selected groundspeed. The AP can fly a route at medium level but has no vertical nav function and cannot fly a procedure of any sort. I believe auto ILS was envisaged but never cleared for use.

[orca]

The Super Hornet can indeed fly a route of waypoints and is capable of 'coupling up' to fly an automatic approach to the boat. The various pilot relief modes also include auto throttles both for en route and in the landing pattern.

I forget what the currency restrictions were, but suffice it to say that you weren't allowed to use the automatics to land until you'd mastered (and remained current in) the mandraulic approach...not something I was ever in danger of.

[just another jocky]

Tornado GR1 auto-ILS worked fine but yr correct it was never cleared. :oh:

Never tried it on the GR4 though.

[CharlieJuliet]

Later Lightnings had a very good auto ILS. Would track localiser and glidepath accurately and had an auto throttle which held 178+/- 3 knots (as I recall). Rumour had it that a senior officer went into the barrier having failed to disconnect the auto throttle after landing from an auto ILS/auto throttle approach !? Anyone got more info on this?

[AutoBit]

Stilton,

Best way to help is maybe to give you a typical profile in a FJ. T/O and climb are normally flown manually. No need for A/T as the throttles are left at Mil power. At the TOC the autopilot can be engaged in an alt hold and heading hold mode. A/T can be engaged to hold the current speed (although I know some FJs have selectable A/T speeds). For small turns Hdg Sel can be used, and for long track legs you can fly direct to the waypoint. At the waypoint Hdg Sel can be selected to turn towards the next waypoint, or in Hdg Hold mode the pilot flies the a/c with the stick but when released the a/c rolls wings level into Hdg Hold again.

At TOD the A/P and A/T are disconnected and the a/c flown manually for app and landing. There are some relief A/P modes that allow a certain pitch attitude to be held, and these can be used if the approach starts to get busy. A/T can be used for the landing and approach (say to maintain 250kts in busy airspace), but that is up to the pilot. Many of us prefer to use manual throttles for landing as ironically enough its a bit smoother. We don't tend to have VNAV like an airliner so there isn't a VNAV PATH option, although as more and more jets get RNAV that may change.

Auto-approach is available in some a/c, but needs specific equipment to be serviceable, and given that it saves fuel, most FJ landings are visual approaches hand flown. Hope this helps.

[Courtney Mil]

F4, F15 - just a basic AP. F3 - cut down airliner AP. With auto ILS, and auto throttle to touchdown, but we weren't allowed to us it; unproven snag with the Radalt detecting the nose wheel or some such bollocks. Typhoon - as you might expect.

[stilton]

Very interesting, thanks for the informative replies, I'm surprised that autothrottles have been around for some time in fighters but I can see how it makes sense.


Couple more questions, any of these autopilots have a vertical speed / ias hold mode for use in climb or descent and lastly does your on board nav data base contain named civilian waypoints or even airways that you could proceed direct to or navigate on ?


I would doubt you would have a civilian data base like that as It would use up so much memory that you want for the military mission,I suppose you don't fly routes or to waypoints like us civilian types but just curious.

[BEagle]

I recall reading a green line entry for the AP in on of the crows' jets at Wattisham (after the sqns had merged): 'Use with caution as +4g pitch excursions may be experienced'.....:eek:

Never used the wretched thing, except in the simulator to play with 'stick top steering'.

As for the switches spattered around the cockpit which were supposed to control the Buccaneer autopilot........:rolleyes:

[Bigpants]

Stilton, while on 31 Sqn I did take the GR1 along the odd airway and do a little procedural work but it was not great and required planning and loading into a tape.

At that time Bruggen did sometimes use civil airports like Dusseldorf as diversion options but when poss preferred a local military base like Norvenich, Gielengkursian (spelt wrong sorry) etc.

[Swil]

Talking of F700 entries, I snagged an F3 autopilot once for " aircraft climbs/descends +\- 200ft with altitude mode selected" only to get the rectification response as " NFF, fault could not be reproduced on the ground". No sh*** Sherlock!! and We all know what NFF means!!

[AutoBit]

Stilton,

I think some FJs have a V/S mode (Tornado?) although none of the ones I've flown have. As for IAS hold, if you mean something like FLCH on an airliner, to the best of my knowledge no they don't….again at least not on anything I've flown.

[Firestreak]

CJ you're absolutely correct, the Lightning had a very good autopilot (Smiths MK 10 I seem to recall), You could use it either in Ht & Hdg mode or in Attitude Hold. In either mode you could select the autopilot and then fly the a/c on the 'little stick'

The incident you refer to did indeed happen. An Air Commodore (I think) wanted to fly the a/c solo and duly underwent a short course. Your first solo was at that time flown in the T4 so off our hero went. On finals to land, he decided to use the autothrottle to keep the speed @175kts but forgot to disengage on landing. He kept pulling the throttles back, not an easy task against the clutch, as soon as he released any pressure on the throttles they moved forward again trying to keep 175kts, the autothrottle won and the barrier saved the day.

The auto ILS was super, so accurate that the decision ht for an auto approach was lower than a manual ILS. There used to be a bit of discussion at Wattisham about the possibility of doing an auto ILS at Honington if you were really caught out by the Wx and lack of fuel and just letting the a/c hit the ground, Honington having an in-line ILS al the time, would have been quite exciting but some folk were quite certain they would give it a go.

[just another jocky]

stilton - the GR1 had a Mach Hold setting. With this, you were free to move the throttle and the AP would vary the attitude to maintain the Mach number - usually used in the decent, though rarely.

The Basic Mode of the Tornado AP also allowed you to simply engage AP with no other modes selected and it would hold the attitude selected. If it was very close to straight & level, it would automatically select straight & level for you (can't remember the range I'm afraid).

There's no "database" on the GR (or F3 afaik). You get a moving map with selectable scales on the GR so you can at least point towards it, you also have access to TACAN display, though not VOR. So whilst not strictly speaking legal to flying in Class A, in the past it was done fairly regularly. Main problems occurred when you were asked by ATC to steer towards some arbitrary beacon and you couldn't find it on the map to head towards. On my GR1 IRET, I flew an airways leg and a full IF approach into Stansted.....all from the back seat too! :eek:

[thing]

the Lightning had a very good autopilot When Binbrook was running down a few plumber mates and I (I was avionics or flight systems as it was then) blagged a ride in the sim. The boys flew it with varying degrees of success and then it was my turn. They were all amazed at the accuracy with which I flew it and of course I basked in their accolades, although I did forget to mention purely accidentally that I flew almost the whole sortie with the autopilot in...:ok:

Edit: I do remember the sim techs didn't like you slamming the throttles open, did something nasty to their magic boxes apparently.

[Dominator2]

Although not the best in the world the Tornado F3 autopilot was OK. Like all things, you had to know how to operate it to get it to work for you.
It was capable of:
Height hold
Heading/track steering
Route flying (both MC Route and JTIDS Route)
Mach hold (good for climbs and descents)
Auto throttle
Auto ILS (not cleared in RTS but very good. Could fly a 67 wing approach better than most pilots)
There was a plan to introduce a much more powerful AP to enable dynamic hands off flying for night/IMC intercepts/VIDs etc but like many things the money was pulled by MOD for other projects.

I flew 3500 hours on F3 and used the AP whenever appropriate. Why not reduce the workload and increase brain capacity for other tasks?

The F3 did have Twin INS fed by GPS and monitored through an MC. Although not as easy to fly down the old VOR based airways it would be easier to fly Rnav routes and procedures if cleared. Also difficult to legally fly a VOR or NDB approach when neither fitted. Very few knew how to use Tacan for VOR Approach!
Not sure about Typhoon but most probably still using "British Officer Coming Through" principle.

[stilton]

Thanks again for the great replies, very interesting.

[stilton]

What is a '67 wing approach' ?

[Exascot]

A very interesting thread for me as a 'heavy' FJ pilot (Ret'd).

Do the 'elite' think that there could be, or is, technolgy to fly in formation on A/P? This is not a joke but it would certainly have helped me :hmm: Never could hack it. Jolly dangerous and classifies as an airmiss as far as I am concerned.

[Timelord]

Stilton,

The Tornado wings move. Although they can be set anywhere between fully forward (25 deg sweep) and fully aft (67 deg sweep) only three positions are released: 25 (take off and landing) 45 (everything else) and 67 (airshows and running away).

Because the wings might get stuck in any position approaches are practiced in 45 and 67. As you might imagine, 67 gives a very high approach speed and alpha.

[Dominator2]

As Timelord states, A 67 wing approach was flown at high speed and AoA. The approach speed was sometimes only 3 kts below the Max Gear Lowering speed. On approach the aircraft nose was so high that some found it difficult to see the runway unless they motored the seat right up. The approaches were even move interesting when flown from the back seat!

[27mm]

No big deal in the F3, as one used the HUD video on the rear cockpit tv/tab.....:cool:

[Fox3WheresMyBanana]

Do the 'elite' think that there could be, or is, technology to fly in formation on A/P?

Some boffin originally proposed this for Tornado. I believe every pilot consulted either died of fright or died laughing. The idea was dropped very rapidly.

67 Wing approaches - grass either side of nose = runway must be under the nose!

[Dominator2]

27mm All very well unless the nasty front seater turned down the HUD Brilliance!

[27mm]

Too true, or even worse in the F2 or early F3s where there weren't no HUD vid.

[just another jocky]

GR1 had nothing in the back other than head down instruments and a big bank of gauges directly in front of yr eyes blocking the forward view to help you. Teaching visual circuits from the backseat was a feat.

GR4 brought HUD & FLIR in the TV Tabs so much easier.

[Danny42C]

Fox3WheresMyBanana,

"......67 Wing approaches - grass either side of nose = runway must be under the nose!......"

True ! But you can't see the elephant/camel/water buffalo etc on the runway in front !

(Trials and Tribulations of an old long-nosed single engine man).

D.

PS: Like the idea of formation on autopilot - but if you don't mind, would prefer to watch from a safe distance ! :ooh:

[Fox3WheresMyBanana]

If I had been unlucky enough to encounter elephants, camels or water buffalo in rural Lincolnshire.....:uhoh:

Actually, we didn't touch wheels on the heavyweight, single-engine 67 wing approaches. The speed was too silly (229kts rings a bell) and would have been very expensive in tires. I don't think it's ever happened for real.

[27mm]

Fox3, 67wg and single engine, now that is gamey! BTW, an F3 was landed from an actual 67 stuck wg app at Coningsby; IIRC, around late 80s by a certain NI driver, but that's another story.....

[Dominator2]

F3- The only benefit to doing a 67wing/single engine heavyweight would be to get all of the BTRs in one go. I fortunately never flew with a QFI/IRE who thought that was a good idea, although I believe there were a few out there!
They are most probably now with some airline trying to incur pain on some young innocent (and maybe incompetent) FO.

[just another jocky]

There have been at least 2 GR swept wing landings that I can think of, possibly there have been more.

GR basic speed was 201kts + allowance for fuel/stores.

ISTR somewhere around 2 tonnes of fuel put you above gear lowering speed in standard fits.

[Onceapilot]

JAJ,

never mind circuits, you should have tried teaching dive/strafe from the back of the GR1.:uhoh:

OAP

[just another jocky]

OAP

I can imagine, but at least all you had to do was not hit the thing you couldn't see (the ground), on a demo roller, you actually had to touchdown, preferably on the concrete which you couldn't see and at a speed on a landing that would give you a chance of stopping.

All good fun! :ok:

edit: of course I didn't mean landing from a swept approach, just landing in general from the back seat.

[ACW342]

JAJ - OAP

whilst at Bruggen and Leeming, when I heard the call on the Hadley box - "C/S 3 miles 67 swept to roll" I always made sure that the RWC caravan door was open and clear of any obstacles.

A342

[OK465]

GR basic speed was 201kts + allowance for fuel/stores.

That's 2 knots below the basic weight speed for our two-seat F-105Fs with the wings as far forward as they would go. :)

The old F-105 actually had the best basic auto-pilot for heading, altitude or attitude hold I ever saw in a fighter aircraft. No coupled approach capability and no auto-throttle of course. No fix-to-fix nav as such because there were few RNAV fixes defined at the time anyway, but one became semi-skilled at TACAN radial/DME point-to-points within reasonable tolerances.

As far as coupled ILS capability in fighters....

....Was in the back seat of a Guard F-101F on an FCF at Niagara Falls one day, and when the USAF advisor doing the check gets to the recovery he says "Let's check the coupled ILS capability." LOC intercept was reasonable with some minor 'S' turns but when we got to GS intercept, the VooDoo briskly pitches down about 10-15 degrees :eek:. Captain Obvious disconnects, and says, "That's not right." Fortunately we didn't have enough gas to try it again.

My 101 checkout was to start in about 2 weeks, but got an offer to go fly a fighter with only a yaw damper, no auto-pilot, and at that point this seemed very appealing.

[glad rag]

Hmm few rusty neurons motivating now, seem to remember the Luftwaffe final "test job" at TTTE was a four ship formation landing with max reverse thrust/ braking starting at the back with a fixed point pass/fail :eek: ....but they had it cushy with full use of high lift....we line swine got the nod to come and watch as it was bloody impressive and Germanic, 'natch.

a F3 did a 67 landing at LEU mid 2000's[think] entire TASF was outside watching the drama evolve, it only stopped when it caught the bottom end cable having exhausted all other possibilities.....

[Courtney Mil]

What is a '67 wing approach' ?Old F3 crews in a bar in Las Vegas hitting on local girls whilst pretending to be born during or after 1967. Never worked.

[Treble one]

Stilton, I'm not an expert but I believe 67 degrees is the maximum sweep of the wings on a F3/GR1/4-a configuration that is used for high speed flight.


Normally, a landing would be performed with the wings fully swept forward (increased lift etc at 23? degrees) without any issues. However, should the variable geometry control in the aircraft go U/S then you may be 'stuck' at 67 degrees of sweep, and you have to get the aircraft on the ground.....


So I guess this was practiced in the sim and (possibly)in the air, like other in flight emergencies.

[just another jocky]

111 - both the sim and in the air....a routine BTR (Basic Training Requirement). The numbers you are looking for are 25/45/67, though with the larger Hindenbuger underwing fuel tanks, there is a limit of 63 on the wings to prevent taileron/tank interaction.

[Treble one]

Many thanks for the confirmation and numbers just another jocky.


Sounds like an interesting landing

[orca]

Now, let me make this perfectly clear. I love thread drift. I think it's inherent in threads in the first place. I find it incredibly tiresome when the inevitable cry of thread drift, usually with a plea for moderators to close the thread, comes from the self appointed policemen of pure and polarised discussion.

I just wanted to point out that someone asked a question about autopilots on modern fighters and within 2 pages we were discussing Tornado wing sweep and BTRs. Where to next I wonder? Give it two more pages and we'll be discussing our favourite kebab vans.;)

[LOMCEVAK]

OK, back to the thread! In the late '80s we flew a trial on the auto ILS mode (APP) in the Tornado GR1. There were two problems: First, the gains for the drive laws varied as a function of the rad alt signal and, as has been mentioned previously, the early rad alts locked up to the nose leg when the landing gear was down. This then resulted in the wrong gains being used by the autopilot and erratic localiser following. However, later standards of rad alt solved that problem so this was not insurmountable.

However, the bigger problem was that the system used the selected course (set on the HSI) and heading, rather than track, to maintain the localiser. Basically, when the aircraft was on the localiser the AFDS turned the aircraft to match the heading with the set course. Therefore, if there was a crosswind the aircraft flew inbound displaced downwind from the localiser. We recommended having a crosswind limit for coupled approaches (and I think that about 20 kts would have been feasible) to limit lateral displacement such that a sidestep could be flown from Decision Height and a landing could be made. However, 'the Company' solution was to adjust the course setting by a factor of the drift angle (can't remember exactly what the factor was but 1/2 comes to mind). The scope for getting it wrong was monstrous so we would not endorse this but we could not get support for the crosswind limit option. However, without any significant crosswind it worked quite well.

The F3 had the same system as the GR1 and the GR4 does also. I have tried it in the GR4 sim and it usually ends up with a divergent oscillation down the localiser but in fairness it is not cleared in the aircraft so the drive laws in the sim were never required to be refined.

[27mm]

Jocky mate, don't forget 58 sweep.....:cool:

[stilton]

Trivia question, could slats / flaps be extended on the Tornado unless the wings were fully swept forward ?

[just another jocky]

Flap and slat at 25, slat only beyond that up to 45, nothing beyond that.

[Onceapilot]

Then there is manoevre flap/slat and 33wing.:oh:

OAP

[Moi/]

^^


Part of the groundcrew funcs would be to sweep the wings, and lower the flaps. I guess always an eary feeling, hoping the Wing Sweep micro-switches were set correctly...


I heard that they have been lowered with them rearwards...but that's engineering for you... It if can be fitted the wrong way, it probably will be..

[Moi/]

On a similar tale...


Jags... installed a relay, however did not polarise it. Cue undercarriage funcs... instead of funcs at a lower pressure, full pressure... Main Leg through door..

[LOMCEVAK]

OAP,

I think that you mean 35 wing.

[Dominator2]

Since there was no detent, he was allowing for parallax!

[Onceapilot]

LOM,
Depends how heavy you are.;)

OAP

[stilton]

Great information Gents, thank you.