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Take-off technique in light singles and twins

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Take-off technique in light singles and twins

Old 28th Apr 2020, 12:03
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Take-off technique in light singles and twins

Australian Flying magazine May-June 2020 published an article by Steve Hitchen on his test flight of the Tecnam P Twenty-Ten at South Port, Q'ld.
Certainly seems a flash looking four seater with upgraded electronics and prestige interior.

The demonstration instructor's takeoff technique was similar to that commonly taught at flying schools on Cessna and other light singles in that the weight is taken off the nosewheel during the takeoff roll by early back pressure on the control wheel.

Steve writes that his instructor advised him to:
"Smoothly and quickly go to full throttle and as soon as you have elevator authority lift the nose so that it's about two inches off the ground and hold it straight with rudder. Around 55 knots the aircraft will start getting light on the undercarriage and will lift off around 60 knots"

For ab initio and even experienced pilots, it would be difficult to judge two inches for the nosewheel to be raised above the runway - particularly at night where nose attitude is difficult to judge. The potential for inadvertently using too much back pressure to raise the nose wheel off the ground early in the takeoff run is that it may cause the aircraft to become prematurely airborne in ground effect before it reaches the recommended takeoff speed. That has its own hazards

With any aircraft it would be better airmanship to stay with the manufacturer's recommended take off technique, rather than the instructors personal technique - in this case playing with lifting the nosewheel two inches clear of the runway during the takeoff run? Unless the takeoff surface is soft or rough why lift the nose-wheel early in the takeoff run when there is no operational need to do so?

The Comet jet airliner was involved in 26 hull-loss accidents, including 13 fatal crashes which resulted in 426 fatalities. Pilot error was blamed for the type's first fatal accident, which occurred during takeoff at Karachi, Pakistan, on 3 March 1953 and involved a Canadian Pacific Airlines Comet 1A.

In those days, De Havilland, the manufacturer of the Comet, recommended that during the take off roll the nose be raised at 80 knots and the aircraft allowed to fly off the ground when it was ready - in other words not at a specific rotation speed. The short nose of the Comet made it difficult for the pilot to visually judge nose attitude when lifting the nose at 80 knots - especially at night. It was all too easy to over-rotate. In addition limitation of artificial horizon design often caused the instrument to be unreliable during aircraft acceleration.

. A similar take off technique was used by the RAF on the De Havilland Vampire and English Electric Canberra bomber. The RAF Pilot's Notes for the Vampire F1 stated: "As soon as the aircraft reaches a speed of 60-70 knots IAS, lift the nose wheel just clear of the ground, then at 82-87 knots ease the aircraft off the ground. The date of the Pilots Notes was January 1947. The first flight of the Comet was also in 1947. There was speculation that nose wheel early lift off may have been to cover the case of nose wheel drag build up caused by the nosewheel impacting on slush during the takeoff roll.

Both early accidents were originally attributed to pilot error, as over-rotation had led to a loss of lift from the leading edge of the aircraft's wings. It was later determined that the Comet's wing profile experienced a loss of lift at a high angle of attack, and its engine inlets also suffered a lack of pressure recovery in the same conditions. As a result, de Havilland re-profiled the wings' leading edge with a pronounced "droop", and wing fences were added to control spanwise flow. The Comet takeoff technique was changed following the results of the investigation

It should be remembered that handling techniques are recommended by the manufacturer's properly qualified company test pilots. That includes takeoff and landing. These will normally be incorporated in the aircraft flight manual or AFM. Instructor personal techniques for takeoff and landing that do not accord with the manufacturer's POH could attract the risk of litigation should an accident occur.
If there is no valid operational reason for changing a flight manual recommendation, then be careful what you teach. It could come back to bite you.

Last edited by Centaurus; 28th Apr 2020 at 12:28.
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Old 28th Apr 2020, 13:35
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Are we seriously going to have the debate that easing weight off the nose-wheel in VERY light aircraft is likely to cause DEATH? I'd say it's good airman-ship especially on an unsealed surface.
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Old 28th Apr 2020, 16:00
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Centaurus already made that observation regarding unsealed or soft surfaces, it’s in the C172 POH from memory. I am also advised, but have no experience, that the C210 will not accelerate if you lift the nose below some rotation speed, and you will just travel the length of the runway in a nose high attitude. I don’t know if others are as tender.

It all depends on weight, CG position and elevator authority. A rear CG at MTOW, a hot day and a big elevator could give you grief no matter what you might think. Then there is the little matter of directional stability.
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Old 28th Apr 2020, 22:33
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I don't know know how the many thousands of T/Off's I've done where I didn't raise the nose wheel off the ground early that I come to get away with it!
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Old 28th Apr 2020, 22:44
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Many types of light aircraft such as the Tecnam in the article, achieve improved directional stability when weight is lifted off the nose wheel. The issue mainly comes from the shape of the tire where it is too “square” across the bottom and too much weight on the nose results in the feeling of riding on the backbone of a poddy-calf, for those farmers amongst us.

The other issue with these small tires is that they are near on impossible to balance in some cases and the whole front end of the aircraft will shake until it slows down after a high speed takeoff. The bigger and heavier Cessna style wheels appear to not suffer as badly from this issue, if at all.
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Old 28th Apr 2020, 22:54
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I always appreciate your posts and anecdotes Centaurus. As a low-time pilot they give me offer some great perspective.

I also read the article and was wondering why the instructor gave that procedure. Having never flown a P2010, I found a flight manual online to check on this. As far as I can see the manufacturer's recommended normal procedure is to rotate at 60KIAS.

At the flying school I learnt at we were told to keep controls about neutral during the takeoff run (whilst allowing for cross-wind correction of course) until rotation speed. Soft-field ops are naturally different.

I flew recently interstate at an aero club flying school which seemed to have a sound reputation. The instructor was great to fly with, but I had to question some of the odd (at least to me) items on their school checklist...like checking that the engine was 'ON' after you'd started it! They also insisted on radio calls for every leg of the circuit. When I queried this I was told it was because it is a busy aerodrome, and no further explanation was given.

I suspect that students who learn in that environment are likely to carry those habits elsewhere. Unnecessary radio congestion would surely be detrimental to see and avoid at most places.

In fact, the more I fly at local airports around the country, the more I am grateful for the 'old school' training that I've had which focussed more on airmanship, common sense, and simple checklists that could easily be committed to memory and would apply across most light single engined aircraft.
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Old 28th Apr 2020, 23:15
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From memory the Cessna 182 POH says that for a normal take-off, leave the nose on the ground and lift it at 50-60 kt.

That seems pretty sensible.
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Old 29th Apr 2020, 03:14
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What is a nosewheel??
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Old 29th Apr 2020, 03:19
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Game, set and match to Akro!
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Old 29th Apr 2020, 03:23
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Originally Posted by Old Akro View Post
What is a nosewheel??
It's when they put the tailwheel on the wrong end.
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Old 29th Apr 2020, 07:06
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Most training wheel Vans RV pilots (excluding 10 and perhaps 14) will be advised to get the nosewheel off as soon as practical.
This is mainly due to the propensity of the shoddy RV nosewheel design that can fail because of the fore and aft oscillation of the long stiff gear leg that has a tendency to dig into the runway and act as spring to flip the aircraft over.
Has happened numerous times, and vans have finally acknowledged its shortcomings by putting out a new design front gear leg for RV's.
Big and expensive job though to replace on an existing aircraft.
Mike Seager who does the transitional training for all RV aircraft, teaches that it is important to get the nosewheel of as soon as possible, and to keep the nosewheel off the ground for as long as possible on rollout fter landing.
Mick
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Old 29th Apr 2020, 08:16
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Careful guys the nose dragger trainer fraternity will be up in arms especially the Vans 'A' fansboyz!
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Old 29th Apr 2020, 09:03
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Originally Posted by machtuk View Post
Careful guys the nose dragger trainer fraternity will be up in arms especially the Vans 'A' fansboyz!
What is a wheel?
https://upload.wikimedia.org/wikiped...6flyer1909.jpg

And nosewheels are what you put on the ground first to stop too much weight being put on the big wheels at once.

.
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Old 29th Apr 2020, 10:21
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I have a foot in both camps. I built an RV9a, but wished I had built a taildragger.
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Old 29th Apr 2020, 12:42
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Originally Posted by harrryw View Post
What is a wheel?
https://upload.wikimedia.org/wikiped...6flyer1909.jpg

And nosewheels are what you put on the ground first to stop too much weight being put on the big wheels at once.

.
Put the nosewheel on the ground first? WTF?
Only if you want to hop down the runway like a kangaroo.!
SB
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Old 29th Apr 2020, 13:05
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Originally Posted by Seabreeze View Post
Put the nosewheel on the ground first? WTF?
Only if you want to hop down the runway like a kangaroo.!
SB
I think he was employing a narrative device known as "Sarcasm" :P

But from it seems here this technique is to cover a deficiency in design where they'd rather add in a couple of extra lines to a POH than go back to the drawing board and fix it up properly? At first look without any real reference the first things that come to mind is that the wheel does look awful tiny and would suffer from a lot of shimmy but I can't quite put my finger on why exactly.
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Old 29th Apr 2020, 14:48
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the wheel does look awful tiny and would suffer from a lot of shimmy but I can't quite put my finger on why exactly.
Talking about nose wheel shimmy. Prior to all the new construction that led to Essendon Fields was a one man flying school run by an eccentric whose name escapes me. He owned a clapped Piper Apache that he hired out cheaply (bring your own elastic band to hold the door handle in place).

Some teenage kid managed to get into and start one engine and tried to taxy and hit the cyclone fence at the back of the Apache. The owner went ape and kicked the kid in the guts after the gendarmes caught the kid and held him until the owner arrived. The owner then kicked the female cop who tried to tell him to back off.

We cross-hired the owner's Cessna 150 and the instructor designated to fly it saw the nose-wheel tyre was deflated. The instructor pumped it up to the correct pressure and departed. On landing back at Essendon the aircraft experienced nose-wheel shimmy so serious that the instructor thought there may be unseen airframe damage the shimmy was that bad. He wrote it up in the maintenance release.

The owner who had a short fuse, went mad at him for not only sullying the maintenance release with a defect entry but also for pumping up the nose-wheel tyre to the correct pressure. That was because the owner had deliberately dropped the nose wheel tyre pressure 50% to minimise the nose-wheel shimmy which had been a feature of that Cessna 150 for months. Slight thread drift maybe but over the years there has been some interesting characters who ran flying schools at EN
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Old 29th Apr 2020, 15:03
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With any aircraft it would be better airmanship to stay with the manufacturer's recommended take off technique, rather than the instructors personal technique - in this case playing with lifting the nosewheel two inches clear of the runway during the takeoff run? Unless the takeoff surface is soft or rough why lift the nose-wheel early in the takeoff run when there is no operational need to do so?
I agree. That technique is most likely to be counter-productive except in the soft field case. Rolling resistance on a firm surface is small compared with aerodynamic drag at TO speed. Only when the ground is soft enough to push the rolling resistance up to some figure (ie about that of soft turf) does the extra aero drag penalty of significant back pressure become a worthwhile trade-off - purely from a performance perspective and notwithstanding other considerations such as eliminating shimmy or dealing with potholes of course. Stick with the manufacturers recommended technique.

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Old 29th Apr 2020, 19:06
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Light singles: I teach the student to establish the takeoff attitude when the elevator becomes effective and let the aircraft lift off when it is ready

Light twins: I teach that the aircraft maintains a level attitude with the nose wheel on the runway until rotate speed. This is so that in the event of an engine failure on the takeoff roll the pilot will have the benefit of nosewheel steering to help maintain directional control. The only exception is the Twin Comanche. Because of its very nose high attitude on the ground care must be taken not to hold it on the ground therefore I let it lift off from the ground attitude when it is ready, so no real rotation, and then briefly hold it level in ground effect to let the speed build to a safer value and then climb away
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Old 30th Apr 2020, 02:08
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I agree with Centaurus and I always enjoy his articles , not to mention his genuine wish to pass on information that may well be lost if nothing is said here.
I also agree with Swark7700 and his take on the subject.
Light aircraft instructing was something that I did many decades ago and I remember that many aircraft ( especially the very light ones) would rattle down the runway if the pressure was kept on the nose wheel to the terror of the students. Taking the pressure off did ease the situation sometimes and I always put it down to sh-tty design , the maintenance that plagued the industry in those days or the result of students landing on the nose wheel and possibly bending the structure.
Civil instructors are always customer focused , for the obvious reason and, you try to achieve the goal by using lateral thinking while still trying to be safe.
Some one I once new said: 'Unlike in the military, a punter only gets washed out when he runs out of money, enthusiasm or scares himself enough to give up.'
Some times an instructor will dumb down a technique a bit much and you end up with something like lifting the nose wheel off the ground instead of taking the pressure off the wheel. Of course, sometimes with particularly bad maintenance, the vibration was worse with the nose wheel just spinning on worn out bearings than with some pressure on it!

I also demonstrated aircraft for sale to many greedy investors with more finance than ability and was ( at times ) told to 'make sure you show them that he aircraft performs perfectly'.
One time I had to demonstrate that a Partenavia could maintain altitude on one engine with a full pax complement ( or almost full as I recall all the group potential purchasers were on board).
From memory, the certification requirement was a 1% climb rate at 5000', on one engine ( for a new aircraft).
Well, we weren't at 5000', one engine was at 'zero thrust' setting ( or maybe a little more) and we just managed to get a little climb out of it.
I for one was surprised , the purchasers didn't notice and were impressed enough to lay their money down..

A demo pilot is charged with making sure the aircraft performs and in this case , maybe this is the dumbed down technique that he preached to journalists of unknown ability
to achieve his goal.

Keep the stories coming, Centaurus!

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