Short-field takeoff technique

[ROB-x38]

G'day

I recently learnt the following short-field takeoff technique for the PA-44:

- full power runup brakes on
- everything in the green
- normal takeoff trim but full back pressure on yoke
- as soon as airborne reduce back pressure, gear up, accelerate and climb out at 82kts (Vx).

Like a Vmu test :E Obviously there's no geometry problems with this aircraft and we didn't leave a trail of sparks (dirt) down the runway.

You could feel the nose wanting to come off almost immediately. The ground roll and take-off distance were very short. Quite impressive actually.

I was just wondering if this is normal procedure on other aircraft?

FYI this is the 1st twin i've flown and on all the singles i've flown the technique was 1st stage of flap and earlier rotation.

Rob.

[compressor stall]

Been a few years since I set foot in a Pa44, but is the technique in the flight manual? If so, fine, if not be very very careful, cos if you get it wrong, even just a bit and can walk away, then you might have some serious questions to answer.

The other thing to remember, presuming that it's a technique in the flight manual etc, is that it does not get you to the single engine best rate of climb speed any faster. Infact the opposite might be true.

CS

[Bevan666]

Sounds like fun being a test pilot. I dont recall reading about that technique in the POH.

You'll be lifting off near Vs and pulling up the gear not long after. I hope you dont experience any windsheer in the transition or you'll end up back on the runway with gear in transit (or up).

I'd love to explain that to the insurance company.

Remember most books takeoff safety speeds are based on 1.2 Vs with flaps up. Lifting off at a slower speed means you are reducing all margins of safety. If you approach the runway at just above Vs you will use less runway. Not very smart though.

With the above technique, what is the distance taken to climb over a 50ft obsticle? Not much different than the technique in the book I'd suspect.

Bevan..

[ROB-x38]

DA and stallie

The points you raise were exactly my concerns. Another concern was a little windshear could have some dire consequences.

Vmca = 56 kts.
Vyse = 88 kts.

To be honest i didn't notice what speed we lifted off at but it was quite slow.

I would suggest it wouldn't say what you've been told as the marging for error is pretty small.
Correct. The AFM suggests a technique similar to what i'm used to. I meant to mention that in the original post.

It is in fact the reason i'm asking. So has anyone else heard of this technique and what are people's thoughts? My thoughts are that it is just pushing the limits a bit...

[maxgrad]

Just to reitterate what has been already well said.
Use the POH and expect less than what it says in take off run etc.
Those figures have been printed for a reason.
You are very correct in wondering at this new test pilot short take off deal.
My advice... stay away from it ....... there are many variables in aviation, lets not make up new, interesting and potentially fatal ones.

[Northern Chique]

Mr Piper already tested it...... and wrote the numbers for a new plane at ISA and as published... most aircraft have aged poorly, have tired engines, and airframes not quite as smick as they once were... the numbers get worse than the flight manual... Id want all the insurance in knots I could get, flying it like the manual says.

[GoNorth]

With full back pressure I would of thought this would of been a rough field take off rather than a short field? :)

[Sheep Guts]

Its all relative really. Doesnt matter if your in a PA44 which I all but 10 hours or a King Air. If you select a small enough field you will constrain yourself and machine.

If you are going to practice short filed take offs ensure you have all escape routes covered. Clearway, obstacle clearance etc. etc. Because if per chance you end up wallowing around at VMCA or under, you need a plan of action. No planning is lunacy!

Remmember because your in a twin doesnt mean an automatic out. It most certainly with no performance means a controlled ditching. My colleagues in my Company operate at high altitudes in the Mid Asian region in king Airs. Even at high altitudes in King Air Im talking 8000 elevation airstrips, an engine failure on take off usually incorporates a ditching unless in excess of a V2 speed is achieved.

So what Ive mentioned above comes down to one letter "P" for performance. If you have "P" alls well then good but if you dont, alterior plans need to be made.

P for performance ladies and gentlemen has the last word. Recognising its demise or increase quickly is the key to survival.


my 2 cents worth

Sheep


P.S. If it aint in the book dont do it. Why? Because it aint documented means it aint been researched, which means insurance companies aint going to listen to your excuse.

[Curved Approach]

yeh i did my twin training in a seminole fairly recently and stuck to the book!! safest and really does get u the best performance (with that nice safety margin).....so the book says:

-Flaps up, trim takeoff range
-On the brakes
-Full power (greens)
-Accelerate to 70 kts (during this role we used to take up the strain so to speak by gradually increasing back pressure, this leeds to a nicer lift off ;))
-Rotate firmly to achieve 75 kts thru 50ft
-accelerate to 82kts for obstacle clearance GEAR UP
-or- accelerate to 88kts if no obstacles GEAR UP

There is the allowance for a flap 25 short fielder which from memory i never did, never needed to.

cheers,

[poteroo]

For what it's worth, the original post mentioned full back stick from brakes off, which I think is the real weakness in the technique proposed.

All this achieves is a lot of drag from elevators initially, then from the wing as the AoA increases, but at well below Vs. It's unlikely this technique will give you fastest or shortest take-off.

As Curved Approach has mentioned - use the best lift flap setting as per the POH. This will give you a better performance, and safer too. (if there is no recommended t/o flap setting in the POH - then you are back in 'test pilot' mode.)

If you, as a genuine test pilot, wanted to try the flap technique, then you might try it this way. This suggestion attributed to very old bushie Aztec pilot met in 60's.

Apply full aileron in any direction, and lower flap to just a tad less than the full down aileron deflection - which will be near as to best flap setting for t/o. Return ailerons to neutral and conduct take-off as recomm. by Curved Approach

happy days

[ITCZ]

I'm with GoNorth, that original post sounds like a SOFT field or rough field technique... minimum ground roll (TOR), which would result in a longer TOD to 50'.

[ITCZ]

Dusted off my 1978 Seminole PA-44-180 Information Manual....

The technique you were shown is neither a soft/rough field procedure, nor a max performance takeoff procedure. Without a p-chart for that technique you nor I have any idea if it is REALLY better than the book technique.

Remember that it doesn't really matter to a professional pilot if the aeroplane can clear the obstacle both engines operating. You should be planning to clear it if the worst situation presents itself.

So...

Normal (recommended) takeoff procedure is zero flap. Manual states that this results in best flight configuration should EFATO occur.

Best takeoff performance (shortest distance to clear 50') achieved with Flap 25. Rotation at 63kt and climb at 67kt to the 50' height.

Compare this to the flap zero rotation of 75kt and BROC 88kt for normal TO.

Consider also that the procedure for EFATO with speed below 75kt is to close throttles and land ahead.

Should EFATO occur with Flap 25 set there is no climb performance information in the manual for the flap 25 configuration. All climb info is for Flap 0.

Guess its not a transport category aeroplane then!:sad:

So what does it all mean?

If you are obstacle limited, first do your charts on a flap zero takeoff and see if you have enough runway. Don't drag the stick into your gut, that's not the technique in the manual.

If you need to use flap 25 to clear the 50' obstacle, where are you going to put it down if you lose a donk after takeoff and prior to 75kts? Have a plan, my 2c worth, pick out somewhere long, clear and smooth within 30 degrees of runway heading.

If you are trying to get airborne from a soft or rough field, don't do it if you are also obstacle limited. Your technique has you spending a LONG time in that no-mans-land of being airborne, possibly below the 57kt Vmca and nowhere near Vyse.

I have been told and had shown to me, lots of different 'techniques' that the other guy thought were quite clever or fun or impressive, but really were flawed as to -- why would you use them?
:hmm: I think your mates demo might be one of them.

[ROB-x38]

OK....i've been waiting for replies from a few different people. Thanks for the input. Now just to clarify and acknowledge a couple of points....

- It's good to have another technique in the old sky rocket, but it's a technique which I will leave as the last resort. Totally agree with everyone's comments re: sticking to the flight manual.

- I'm well aware of the dangers associated with light twins. Performance figures offered in AFMs are under ideal conditions with perfect pilots and new aircraft - realistically a rare situation, so why push it?

- There's been a couple of mentions of insurance companies, which although valid points, I don't think is the real issue.

And finally, ITCZ
I have been told and had shown to me, lots of different 'techniques' that the other guy thought were quite clever or fun or impressive, but really were flawed as to -- why would you use them?
I get the impression you think this was me and a buddy out being idiots. Perhaps I should have clarified earlier, this wasn't some manhood comparing exercise, but a technique shown to me by my instructor during training. And i think you and GoNorth may be correct re: soft/rough field takeoff technique, perhaps that's what was being demonstrated.

Anyway, thankyou everyone for the replies, this pprune thing really is a great resource! :ok:

Cheers

Rob.

[compressor stall]

There's been a couple of mentions of insurance companies, which although valid points, I don't think is the real issue.

When you are sued by the insurance company for flying the aicraft negligently by op;erating outside the instruction book (flight manual) and causing $X00 000 damage and you need to sell your house, car and the children for scientific experiments, you might think differently. :{

[itchybum]

ROB-x38, in a slightly different direction, all I can add to the good material already posted is that a rough or short field technique is naturally going to be carried out on some sort of, well, rough field.

The point is, be careful when running up the power at a standstill. The vortices around the prop may lift the small stones found on an unprepared surface into the propellor arc with resultant damage to the leading edges of the blades. The damage can be filed away (by a LAME?? Pilot?? not sure about pilot, good CPL theory question, I suppose) but only so far.

Hope you find that useful !

[Curved Approach]

Exactly.....re-read the posts carefully!!!!!!!! That technique of full backstick is not anywhere in the manual and for all we know could be resulting in worse TOR and worse TODR!! ITCZ is right in all of what he says. Plues the seminole is a fairly poor performer really and to add to that with a flap 25 take-off!

And i quote my 1978 manual page 4-19 (revised july 24, 1981 :))
The performance shown on charts will be reduced by uphill gradient......rough or grassy surface, OR POOR PILOT TECHNIQUE" I guess if it works for you...:hmm: but from my experience it does leave me thinking riiiight, cant you ask your instructor or whoever showed you this if it was a soft field technique that they use?? by all means on a soft field mayb about half to three quarter backstick when you are gettign the aeroplane moving ... maybe this is why you could feel the nose wheel rising and wanting to fly as it was just coming out of the soft field ;):p

[ITCZ]

Rob, fear not. If I was sledging you, you would not need to guess ;) Just ask Kaptin M or AirNoServices, etc!

No ridicule intended.

Perhaps it would be better for me to say, that a healthy skepticism is a good quality in a pro pilot.

We are in an occupation where we are playing with our own life and that of passengers. Technique not in flight manual? Not necessarily wrong, but be suspicious.

In this instance, I think you should get back to your instructor and get him to show concrete facts to support the technique he is teaching.

Imagine yourself in a court of enquiry one day. One or more judges running the show. A $2000/hr lawyer asking you 'And this technique, Capt Rob, which technical document did you base it on...?

Like I said, no ridicule intended.

Another thing that bothers me --

but it's a technique which I will leave as the last resort

Unless you are being pursued by crazed Moro tribesmen that are going to feed you your own scrotum, then kill you, I can't think of a suitable time to use a 'last resort' takeoff technique.

Maybe i have misunderstood your choice of words, but sometimes, you just don't launch. Thats the job. When to go, when to wait, when to try another angle, when to dig your heels in and say "No, not today, not on my licence."

For your own benefit, get an exact understanding of what this technique means in terms of TOD, TOR, Vs, Vmca, time spent accelerating to Vyse, RoC, EFATO considerations, the whole lot.

FWIW, good thread. :ok:

[ROB-x38]

Definitely appreciate all the replies, you've got the cogs turning. I think it's clear that i'm a low hour pilot in the thick of my training and learning all the time. With all the AFM bashing (esp. re: engine handling) it's sometimes difficult to distinguish the good from the bad.

So basically the 2 main dangers with deviating from the flight manual with takeoff/landing procedures are:
- reduced safety margin (in this case)
- who knows how it will perform.
ie: sticking to the manual at least you know where you stand.

Unless you are being pursued by crazed Moro tribesmen that are going to feed you your own scrotum, then kill you, I can't think of a suitable time to use a 'last resort' takeoff technique.
Agreed, that was a bad choice of words. Of course you should never be in a situation which requires using this technique. It's the old "A superior pilot uses superior knowledge and airmanship to avoid using superior skills." ie: I should of known there was a crazy scrotum-feeding tribe in the area and not stopped in the first place ;)

Cheers

Rob.

[QSK?]

An article by John Deakin "Short and Soft Field Take offs - FAA vs Reality" may also be most relevant to this topic. Go to:

http://www.avweb.com/news/columns/182089-1.html

[Woomera]

And that say's it all :ok:

Print it off and take it to your instructor for a discussion, I'm sure you will both learn something.:)

[Tinstaafl]

Unless I misread J.D's article there's a point I disagree with. For obstacle clearance he seems to be advocating that - given more runway than the ground roll requires - the a/c be kept on the ground until some speed higher than Vx (or maybe accelerated after lift-off to some speed >Vx) THEN the a/c is zoom climbed, trading speed for height.

If that's the case then there's an error in his method: Any speed greater than Vx is wasteful of energy due to the greater proportion of drag reducing the excess available for climb. Think of the power & thrust required/available curves.

Have I misread something in his article? Or am reading more into it than he intended?

[Curved Approach]

I havent read JD's article but that does sound odd Tinstaafl....the only thing i can think of similiar to that would be a V2 overspeed giving us better performance from the 2nd segment on.

In smaller aircraft this zoom climb technique gets u thinking, why would you want to be remaining on the runway chewing it up for emergency use and then zoom climbing when you could take off as usual and have gear up already ad be climbing and accelerating away.

hmmmmm

[poteroo]

John Deakin's Article

Have to agree with Tinstaafl that this article is more than a bit wobbly.

He seems to be confused about a few things.

Firstly, a rolling start will give you quicker acceleration than the training method of stand on the brakes and feed in full power. On reasonably wide strips, you should start these from the 'downwind' corner, heading slightly toward the upwind side of the runway. You'll be 10kts ahead of the traditional method at any given distance.

He never mentions load anywhere. Why not dump some weight if the strip is so short?

His suggestions for full flap t/o, followed by a gradual change in configuration and acceleration at 6 inches height - leaves one thinking it's again test pilot stuff. One change in the wind gradient and JD is history!

As for leaving the aircraft on the ground beyond when it will fly - this is contrary to all we know about drag and also u/c damage. It will accelerate faster if airborne, all other things being equal. If the strip is at all rough, the less time the wheels are rolling - the better.

All in all - the article does more to confuse than clarify, and I can't say that I'd be recommending it to any student as background reading on short field operations. About the best thing he suggests is to find yourself an experienced bush instructor to learn this sort of stuff.

happy days,

[Tinstaafl]

V2 overspeed still doesn't take you past Vx. That method is used in jets (where Rwy length is available) to get closer to Vx for the climb.

I use the rolling start from downwind taxi a lot ie power applied as I turn the corner from one side of the airstrip.

The goal is to accelerate & rotate to achieve Vx then flap & gear as soon as possible. Maintain Vx & full power until clear of the obstacle. Some strips I go into require a turn almost as soon as airborne.

If a soft, boggy or rough field then that will adverserely affect distance required. No getting around that. Get the thing airborne in ground affect as soon as you can - but not below Vmc - then accelerate to Vx & as per before.