Flaps on aborted takeoff ?

[Teroc]

Heres one for you all...
Scenario...
In a small single engine aircraft (cessna 150/172 etc etc) for some reason you dont get the takeoff performance you require and that hedge at the end is getting far too close....frighteningly so !!...

A friend of mine said he would immediately extend every last bit of flap he has, whilst simultaneously cutting power and braking... his thinking being that once over the "lift" flap settings and into the "drag" flap, more weight would be placed on the wheels therefore ensuring better braking performance and more drag on the aircraft leading to shorter stopping distance..
Personally i'd be afraid that whilst travelling through the first 20° of flap sufficient lift may be produced to get you airbourne leading to all sorts of problems...
What do you guys think of this ? .. any merit to the idea ?

Teroc

[BEagle]

As speed decreases, maximum wheel braking is the thing which will help most. Whilst full flap might increase drag, the sudden lift increase could prove embarrassing!! I suggest that closing the throttle and braking as hard as you can without causing the tyres to skid would be your best course - once you have started the deceleration, carefully moving the control column back will help increase the 'weight' being carried by the braked wheels and hence the effective braking of the aircraft.

[EESDL]

A serious question, but before I start, Do C-152s have bang seats?

Sorry couldn't resist, I mean it's getting late and I'm stuck in front of a *ucking PC, you do the maths..

Has this scenario been tried out, with markers at the side of a huge runway, obviously.

[This message has been edited by EESDL (edited 05 April 2000).]

[Angle of Attack]

I'm afraid by extending the flaps in this matter the entirely opposite would occur. Sure extending the flap beyond the 20 degrees or so would increase the drag but as flap increases lift increases continually. Sure the drag increases but drag is a minor contributor to stopping a C172 at such a low speed. The way to stop the aircraft fast is friction between the tyres and ground and braking. With an increase in lift, there is less weight on the main wheels, less friction and less braking effectiveness, and more stopping distance. In fact the technique used when landing on short strips in bush areas is, as soon as touching down from a short field technique landing is retract the flaps fully, full back pressure and maximum braking without skidding, and I can guarantee this will stop you the quickest.

[Hugh Jarse]

Take a look in the A/C manual. If it's not a recommended procedure, it's unlikely to give you better stopping performance. Remember these A/C are certified by test pilots that put them through manoeuvres that you or I are unlikely to ever do.

------------------
JARSE! Pull and rotate 90 degrees

[foxmoth]

If you have the extra capability of thinking about flap whilst carrying out an abort, you are either VERY good, or very stupid to think you can manage this as well as trying to control and stop the aircraft, unless you are very current and have pre planned the manouver. Having said that, I would agree with those that say you are better off RAISING the flap rather than lowering it - thus putting the weight firmly on the wheels.

[This message has been edited by foxmoth (edited 09 April 2000).]

[Risky.Flyer]

K.I.S.S

[Fokjok]

When you reject, the most important thing to do is to START LOSING SPEED. Therefore, immediately, select idle thrust (reverse if you have it), and maximum braking.

To get the most out of the brakes, you need the weight of the aircraft to be supported by the wheels not the wing, so the appropriate action is to retract the flap. On a big aircraft, the spoilers will deploy automatically or will be deployed manually. This ensures that the weight is on the wheels.

Obviously, there is a danger on some types (eg Barons of some vintages) of confusing the flap control and gear lever - but then if you retract the gear, you will stop more rapidly - and before you all laugh at this, there is provision for deliberately retracting the gear on the ground in many large transport aircraft.

If you hit the hedge at 40 knots it will do a lot more damage to you and the aircraft than if you hit at 20, so give serious thought to all of this.

Needless to say, having cocked it up by mis-calculating your performance in the first place, you'll get to carry the can home with you.

[This message has been edited by Fokjok (edited 11 April 2000).]

[Flight Deck]

Lets look at this.

If you’re in a C152/172 you won’t have any thrust reverses as mentioned above.
Your airspeed will probably be low to stop with normal braking, unless you’re using a very short strip. Adding more flap will not solve your problem.
I used to fly C210 in the Outback of Australia. I have never had to resort to any abnormal procedures just to bring my aircraft to sudden stop, just use the POH and safe handling.
If the procedure was to be an important issue for the aircraft type in question, I believe the manufacture would have taken it into account.

[Fokjok]

Flight Deck, yes you're quite right about no reverse on a C152, that's why I put it in brackets!! For those of us who fly with reverse, I mentioned it.

The original question relates to a 'worst case'. You have a touching faith in the manufacturer if you expect the POH to cover every eventuality, and the original post raises an interesting issue.

I would have thought that bush flying should teach you to expect the unexpected and be prepared for it.

You are right to agree that using additional flap is clearly wrong, and shows a poor understanding of the facts behind how energy is dissipated duting an RTO or landing.

The superior pilot uses his superior knowledge to avoid putting his superior skills to the test... Are you a superior pilot?

[This message has been edited by Fokjok (edited 14 April 2000).]

[Flight Deck]

FOKJOK – When flying in the bush, flying issues arise everyday. You do become complacent with your aircraft and locations.
At one point a company pilot advised me to use 20oflap (Normally 10o) for a very short takeoff runs. As there was no P-chart to cover this type of maneuver, I would have been on my own if I had an accident.
My point is, unless your have received proper training or at least know your stuff. I wouldn’t be advising any young pilot to do something not covered by the manufacture or Flight Manual.
An old employer once told me that a P-chart in my aircraft’s flight manual was wrong, I bet if something went wrong he wouldn’t be backing me up. What do you think?
P-charts have been put there for many good reasons, don’t start adding your own just because I sounds like a good idea.
Yes I do have a touching faith in the manufacturer; this level of disciple was explained to me early in my training.

Back to the original question, (In a small single engine aircraft (cessna 150/172 etc etc) and so on.
I have never seen a C150/172 use much more than 10o flap. I wouldn’t touch it at all, just concentrate on stopping.
Normal rotation would be between 45 to 60 kts give or take a few knots, it’s been some time since I have flown one. At this low airspeed it shouldn’t take much to bring the aircraft to a stop.

[2R]

By raising the flaps more weight is on the wheels increasing traction ,thus improving braking action.With no brakes available all drag should be used the doors when open on a cessna provide excellent drag and can slow it down,Test data to follow.I do like the idea of bang seats,however they probably cost more than a cessna.When all else fails read the book. :)

[ShyTorque]

As well as opening the doors I also advocate throwing out all baggage (less mass = less for the brakes to do). Also my pilot's case, which I always tie to my left leg with 10 feet of para-cord prior to take-off. This acts as an effective ground hook. With the other spare hand I intend to dial 999 on my mobile phone as it's quicker than expecting ATC to contact the fire section. As 999 may take some dialling I have re-programmed it as 0000001 (or was it 00000001?).

Yes, of course I am joking. You don't think I would seriously throw out all MY baggage do you? Some of it is Italian leather!



------------------
Fly safe!

[Teroc]

Cheers for all that folks...
Good stuff....

Guess i'll ignore my mates advice and go with the standard "Up Flaps" technique :)

Thanks again
T.

[Airprox]

Good Luck

[Flight Deck]

What luck – an aborted Takeoff needs more than luck.