A4 Skyhawk Leading Edge Devices
 

Hi All

I was watching a video of the A4 operating off HMAS Melbourne on Youtube and noticed that as the catapult fires, the leading edge slats(?) very quickly retract.

Link follows and you can see this happen at 4:30 or thereabouts.


Can anyone educate me on what initiates this? Is it airflow over the wing? I imagine it isn't throttle related as I'd assume that full throttle would be in place well before the moment of launch.

Thanks in advance,

Flyer

Can't help the OP with their question, but I do have one of my own.

How did Russell Crowe get into this film? I could swear it's him doing the talk down at about 0.25....

Ahh, Carrier capability...happy days! :ok:

Yeah Buster it's hard to believe it was once true isn't it.

And I love seeing the Skyhawk again. After many airshows I have to say it and the Harrier were the two loudest jets I have ever heard. It may have just been the position I was in or the proximity, but watching a Skyhawk depart from Nowra years ago, the most lasting memory was the sheer volume.

Cheers

Flyer

The slats are operated simply by Angle of Attack. At high AOA (and at rest)they simply fall to the lower position. They come up themselves at lower AOA. The pilot has no direct control over them. Sometimes they retract/lower assymetrically - which is why the Blue Angels fixed them permanently in the raised position. No room for random fluctuations during super close formation...

They learnt that from the Tiger Moth.

IIRC the A4 (TA4J) slats were spring loaded ‘out’; the force of the airflow (proportional to alpha) forced them to close. Thus as speed increased the slats closed, conversely with deceleration or increasing AOA – tight turns, pull ups.
A poorly matched set of slats might deploy asymmetrically giving an interesting rolling motion, particularly at high ‘g’. Such anomalies were rare and the walk-round pre-flight checks required the slats to be pushed in manually with subjective comparison between wings.

No they didn't need spings. They are heavy enough to fall into position at rest. Rolling them during Preflight on the single and t-birds felt the same.

Aaahh -- the A-4!!
 

I flew the A-4M with the USN - and it was one of my favourite aircraft to fly. An absolute delight!!

The slats are purely aerodynamic, extending when needed, and retracting when not. On the ground they are extended thanks to gravity and somebody called Newton and his fixation with apples.

Only problem was with a rapid onset of 'g', when one side might extend momentarily before the other. Fortunately, the canopy was close to your helmet, so a quick smack on the side of the head, and all was then sorted!!

A very capable aircraft, and prematurely obsolescent, in my view.

On of the more disconcerting things about the Australian A4 guys was their SOP of only going to half power on the catapult until the flag dropped. No-one briefed me about this; I couldn't believe it when I was given the ready-to-go signal while I was still winding them up. Full power came on pretty smartly just before the catapult fired.

Did the automatic slats on the F-86 work in the same manner as the A4D/A-4?

Flyer517
 

Most posters are correct, except the one that said they were spring loaded - some may have been, but the A4G definitly were not.

The reason for the slats to move aft so quickly was simply the huge forward acceleration of the aircraft; the slats were simply "hanging out" under the influence of gravity, so when the aircraft started to move, they sort of stayed in place.

Schiller: I can't recall what you mean. There was a little "grab handle" that folded down from the side wall; you were meant to hold that at the same time (and in the same grip) as holding the throttle. That would prevent your throttle hand from moving back under g - it could only be grabbed at full power, IIRC.


Edited to say: 3-wire, should we know each other?

That is untrue. We used exactly the same procedures as the USN. Idle until hooked up (signalled by the FDO - CATO), then Mil, wipe-out the cockpit and check T & P, slute and brace.

And if you ere interested, the RN did the same.

An A4 pilot mate of mine mentioned that the assymetric deployment used to cause a problem during ACT. Often, when pulling high AOA, one would deploy beofre the other and you would get undemanded roll which would sometimes put you in a bad position. The solution, I gather, was to have some duct tape with you during the walkaround and put a strip around the leading edge about mid span which was enough to hold them in. But you had to remember to add a few knots to the approach speed!

Ah no, God provided me with two feet and the Navy encased them in socks, aircrew, for the use of and boots, aircrew, for the use of.
It took a little while, but remembering to coordinate roll inputs with rudder inputs overcame the assymetric slat deployment problem.
Your friend must have been a air force pilot with 10000 feet of runway to land on.

Thanks Arm..
 

Jed_Thrust you answered my next question regarding why it happened so quickly just at that point.

And thanks to everyone else for the replies.

Great looking little aircraft.

Flyer

Just a bit of nostalgia for Three Wire ;)

http://www.eacott.com.au/gallery/d/1...t+cat+1971.jpg

http://www.eacott.com.au/gallery/d/1...t+cat+1971.jpg

http://www.eacott.com.au/gallery/d/1...foreground.jpg

Aahh-h. Thank you John.

My guess is that is CMDR John "Mr Skyhawk" Da Costa on HMS Hermes. And the trade for decktime was a Sea Fury?

3W :D

Not Hermes... Eagle.

Hermes had both cats on the bow (as did Victorious and Centaur), while Eagle had one on the bow and one on the waist post 1964 (Ark Royal had both on the bow until her 1967-70 modernization when the stbd bow cat was moved to the angle, but both cats were fitted with a "horn" extension that is absent in that photo).

Also note that the pic info says "RAN Skyhawk loading onto Eagle waist cat 1970", "RAN Skyhawk launching off Eagle waist cat 1970", and "RAN Skyhawk landing Eagle 1970_ barrier gear in foreground".