Super Etendard - flight controls question

[Pappy]

G'day people,

I want to build a Super Etendard Modernise (SEM) in flights, moments after a catapault launch and banking left, with the wheels coming up.

Apart from the horizontal stabs leading edge down and the leading and trailing edge flaps deployed, how would the SEM achieve a bank?

I realise that with a modern FCS the flight controls could actually have counter-intuitive deflections, but for a relatively gently left bank would it simply be left aileron down and right aileron up? The SEM has perforated spoilers on the upper wing surface, do these operate deferentially or in concert with the ailerons (similar to the F-4) instead?

Noting the twin ventral airbrakes, I don't think the upper wing spoilers are used as normal airbrakes in flight, but perhaps deployed on a landing as additional lift dumping devices,

cheers,

Pappy

[Mick Drover]

Hi Pappy.

One observation from a few SEM cat launches I watched is that in addition to the rear stab full nose down, it also looks like there's a pile of full nose up trim applied too. Something you might want to have a look at if you're looking at flight control configuration just after launch. I can't make out much of what goes on after launch. From most of the video available it appears that it maintains heading for a tim, perhaps allowing for the strop to fall clear??

Don't forget the strop either!

Mick

Edited July 9, 2016 by Mick Drover

[Pappy]

Hi Pappy.

One observation from a few SEM cat launches I watched is that in addition to the rear stab full nose down, it also looks like there's a pile of full nose up trim applied too. Something you might want to have a look at if you're looking at flight control configuration just after launch. I can't make out much of what goes on after launch. From most of the video available it appears that it maintains heading for a tim, perhaps allowing for the strop to fall clear??

Don't forget the strop either!

Mick

G'day Mick,

From what I remember, the SEM has two flap settings, half and full. On land based take-offs, half Leading Edge (LE) flaps and no Trailing edge (TE) flap is selected, whilst carrier launchers requires full LE and TE flap selected. When the full flap setting is selected, the FCS also inputs about 14 degrees elevator trim to counter a longitudinal axis pitch motion (due to the large moment induced by those big TE flaps), but what I don't know is what purpose the perforated upper wing spoilers perform.

I have seen one pic with the jet in a slight bank and the upper wing spoiler slightly deployed. I cannot make out what the ailerons are doing. Perhaps roll control is via ailerons at low speed and then these get locked out above a certain airspeed when the spoilers take over? The problem with modern jets is that they often don't use flying surfaces in the conventional sense, many of these surfaces have mixed control functions, resulting in flaperons, stabilators, ruddervons etc. The SEM is not part of the generation of relaxed static and dynamic stability jets, but (and it is just a guess on my part) the FCS would still require some form of stability augmentation system as ther would be a level of instability designed in,

cheers,

Pappy

[Jure Miljevic]

Hello, Pappy

Probably stating the obvious, but nevertheless ... Just as you described, spoilers get activated above certain speed and act as a primary roll control surface. I would not expect spoilers to deploy at take-off, especially not on a plane, which also feature ailerons. Spoilers induce bank by decreasing lift, and I can hardly imagine situation, when that would be beneficial at low speeds apart from serving as speed breaks after touch down. During take-off, decreasing lift is not exactly what one aims for, especially not if there are perfectly good and substantially more effective ailerons at one's disposal.

At carrier take-off plane can bank slightly because of slight turbulence just after leaving deck or inevitable (if ever so slight) cross-wind in a case of angled deck launch (being catapulted from a hangar deck on Essex class carriers into 90° cross wind during WWII must really have been something to bore your grandchildren with). So flaps and droops full down, elevator trim up, ailerons and rudder at neutral and spoilers flush with the wing surface just after take-off sound perfectly compatible with slight left, or right for that matter, bank to me. Cheers
Jure

[Antoine]

Manuel pilote Super Etendard

[Jure Miljevic]

Antoine,

I stand corrected. As far as I can see, both ailerons and right spoiler are slightly deflected. Serves me right to rely on general knowledge without studying the particular case. Still, why to decrease thrust and increase weight with installation of blown flaps to gain extra lift just to waste it away with spoilers? Also, on this particular photo hook is lowered, so the plane most probably bolted. I am tempted to claim that we are looking at the spoiler still not fully retracted after being deployed as a speed brake at touch down. However, in such a case both spoilers would be deflected.

Live and learn. Studying manuel de vol on the link you provided will certainly help. Cheers

Jure

[John B (Sc)]

At low airspeed, such as just after catapult take-off or an overshoot - 'bolter', applying aileron is likely to provide only yaw, not roll, because of the drag produced by the downgoing aileron. Differential ailerons help reduce this effect.

However, that is why the SEM designers will have opted for spoilers for roll at low speed, as shown in your photo. Both roll methods add drag, inevitably; in this case the spoilers are the more effective way of providing roll. The loss of lift is minor and temporary.

Also at very high angles of attack the airflow over the ailerons with blown flap down will be variable and ineffective in helping roll, I suspect - again looking at that picture. What is flowing over those ailerons is rather well tortured air !

Umm, if that is a bolter - and with that hook down it does seem likely, I wondered about the full up elevator, which is what it looks like. Looking at pictures online it appears that elevator trim must be close to fully wound back on approach. That high nose angle looks distinctly fraught to me though.

I hope that helps.

John B

(Incidentally , note that there is a trace of left rudder on in that shot, suggesting that the pilot wants to stop going too much further in right roll. A busy time for the pilot that, and with a notably nose up attitude I bet he/she is concentrating hard.)

Edited July 9, 2016 by John B (Sc)

[Antoine]

You're right, it's a bolter.

But look at the spoilers on those two.

Check the main page where those pics come from, it's highly interesting.

On the funny side, you can also watch this video where an exchange pilot from the Marineflieger goes from the catapult straight into the water...

Whatever, it's a great aircraft, but the end is in sight... in two days exactly, 12th of july, with a ceremony at BAN Landivisiau, Bretagne.

Edited July 10, 2016 by Antoine

[Pappy]

Manuel pilote Super Etendard

Thank you very much Antoine, a brilliant photo that answers many questions.

At low airspeed, such as just after catapult take-off or an overshoot - 'bolter', applying aileron is likely to provide only yaw, not roll, because of the drag produced by the downgoing aileron. Differential ailerons help reduce this effect.

However, that is why the SEM designers will have opted for spoilers for roll at low speed, as shown in your photo. Both roll methods add drag, inevitably; in this case the spoilers are the more effective way of providing roll. The loss of lift is minor and temporary.

Also at very high angles of attack the airflow over the ailerons with blown flap down will be variable and ineffective in helping roll, I suspect - again looking at that picture. What is flowing over those ailerons is rather well tortured air !

Umm, if that is a bolter - and with that hook down it does seem likely, I wondered about the full up elevator, which is what it looks like. Looking at pictures online it appears that elevator trim must be close to fully wound back on approach. That high nose angle looks distinctly fraught to me though.

I hope that helps.

John B

(Incidentally , note that there is a trace of left rudder on in that shot, suggesting that the pilot wants to stop going too much further in right roll. A busy time for the pilot that, and with a notably nose up attitude I bet he/she is concentrating hard.)

G'day John,

I totally understand the concept of adverse yaw, so diferentially applied spoilers makes perfect sense.I suspected the wing spoilers would be for roll input but was not sure if the ailerons acted as flaperons at low speed. The F-111 used differential wing spoilers for roll input at low speeds and wing unswept (16 degrees). The spoilers were locked out when the wing seep was past 46 degrees and then roll input was input through the stabs. The F-4 used differential spoilers as well as ailerons, but I think that the F-4's ailerons had far more down than up range of motion. Modern jet flight controls do funny things and what seems intuitive is not always correct.

I spotted the (slight) rudder deflection. I agree, that it is to kill the roll moment but the rudder is used to balance the turn so it could just as easily be a right deflection as the speed and bank angle will determine if the turn is balanced.

Thanks for your input as well,

cheers,

Pappy

[Jure Miljevic]

Hi, Antoine, John B and Pappy

According to the manual, spoilers are predominant roll command surface at high speeds and improve aileron efficiency at low speeds with flaps down. Manual does not mention low speed aileron reversal, so differential aileron deflection is obviously efficient enough to prevent this. A few other sources also mention leading edge bleed air system, supposedly installed into SuE and SEM. That would thicken boundary layer and improve airflow over ailerons, but so far I have found no mention of that system in pilot's manual so I guess it had not been actually installed.

Venturing into the field of intuitive again, the only other explanation for right spoiler deflection I can imagine is that left main wheel rolls off the deck slightly earlier than the right one. Angled deck does not end with 90° cut so the possibility is there. However, with the plane barely touching the deck or being already airborne at the end of it I have no idea how much, if any, effect does that have on plane's roll. Cheers

Jure

[John B (Sc)]

Pappy,

Thanks for that information. (and Antoine) My apologies if I sounded like I thought you didn't understand; I was trying to be as clear as I could. Interesting , shall have a look at the manual (historical interest only now the machines are being retired! Shame.)

Do you think that looks an unusually high nose angle? It still looks that way to me ; Jure - what think you?

Cheers,

John B

[Antoine]

No.

THIS, is a high nose angle.

Courtesy of a Marineflieger exchange pilot.

[Jure Miljevic]

Hi, Antoine, John B and Pappy

Was that the Marineflieger someone mentioned earlier? I was amazed to see that after initial nose pitch up SEM's wings were still producing lift. I would expect a plane being flung through the air at such an aoa to drop into the sea immediately.

Locking down spoilers at low speeds and relying on ailerons only would still enable adequate roll and also allow higher maximum take-off weight, but that is just my personal opinion, of course. Anyway, spoilers are, or better said had been, very much in use at carrier take-offs. Going through SEM's carrier take-off videos I noticed that many times right spoiler and ailerons are already slightly deflected while the plane is still rolling on the deck.

Pausing the video and then examining it frame by frame shows slight right spoiler deflection well before the plane leaves the deck. To me that shows that pilot is anticipating roll to the left immediately after take-off and is taking measures to counter it. Just after leaving the deck SEM's flight attitude is exactly like Pappy described it in his original post: slight bank to the left and slight ailerons and spoiler deflection to the right to bring the plane on even keel. Whether the left bank is caused by reasons, listed in my previous posts or something entirely different, still needs clarification. Is there a SEM pilot on this forum? Cheers

Jure

[Antoine]

Maybe it's just to avoid being in the way of the carrier if a splash occurs?

[John B (Sc)]

Thanks Antoine. Yes, that’s nose high for sure! Wow.

I presume the pilot pulled full back stick as he came off the catapult, to get that angle, presumably due to acceleration forces.

That wild rocking and rolling makes me think of the falling leaf maneouvres we used to enjoy in much simpler aeroplanes, at height. Full back stick, let the aircraft start to wing drop in a stall/spin entry, then boot full opposite rudder to reverse it into a spin entry the other way. If you caught the timing right, you could do a series of reverses, quite controllably. Great fun, quite gentle. But only at safe height, not like that.

That looks like rather too exciting a exciting demonstration of desperate use of – mostly rudder - to try to keep the aircraft controllable long enough to get out!

John B

[Antoine]

He was lucky, as he choose the right moment to eject, between two nearly 90° rolls.

Usually, when there's an accident involving a military aircraft, there's a survey report published by the Bureau Enquête Analyse Défense, BEAD.

I've searched and searched, but never found anything.

Must be classified, due to the German Marineflieger pilot involved.

[Antoine]

Another video, with maybe some answers... or more questions!

[andy wood]

Antoine, can I just thank you for bringing to my attention the website that holds the pilots manual. Never knew such a place existed. I can see myself spending many a happy hour there. Thanks once again.

[Antoine]

You're welcome.

I'm pleased to help, but it's nice from you to say that it does.