Rotate or not to rotate.

[Dewdrop]

I fly a 172 from a very long tarmac runway. My question is this,

Instructor No.1 says, "on take off allow the speed to increase with gentle back pressure and the aircraft will fly itself off".

Instructor No2 says, when the ground speed reach's 60mph pull back on the stick and fly off.

Both work fine, but which is better from an airmanship point of view ?

[FlyingForFun]

Do whatever it says in the POH.

I don't have a C172 POH to hand, and even if I did I don't know if the instructions vary from one variant to the next. But, off the top of my head, I'd have thought that the manual would suggest a positive rotation. I think the POH for the Millenium Edition suggests 55kt for the rotation speed. (Do you really mean mph? I thought all C172s measure airspeed in kt, but I'm quite prepared to be corrected if I'm wrong.)

In my limited experience, I'd say the practice of letting the aircraft fly itself off the runway tends to apply to tail-draggers. In a tricycle you would normally rotate positively. But that's only from a handful of types, and there are always exceptions to every rule which is why I say the POH is the only place for a definitive answer.

FFF
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[Spikeee]

I agree with FFF, just use the POH.

Also, your groundspeed doesnt matter its the airspeed.

I have never flown a 172 or any Cessna for that matter :P

[FlyFreeWbe]

What I find, is that I rotate @ 60kts to about a 5 degree angle of attack and hold it. This will allow the aircraft to accelerate to 80kts (climb speed) and then I'll arrest the climb to hold it. Really its kind of a halted way of instructor 1's method with the ingredients of instructor 2's.
I didn't really think about it with airmanship in view before, but it helps reduce workload. Try smoothly puling back and allowing the speed to increase in a strong crosswind!! Instructors @ my school all have the 'get in the air asap' mentality :p
The POH is good too, cant look at the mo - any clues as to what it says??

FFW

[Brooklands]

In my experience a 172 will fly itself off the runway given enough distance, unlike the PA-28 which definately needs a positive rotation. Having said that I normally give a posative rotation a the appropriate speed for the particular mark that I'm flying.


FFF - Yes, some 172s do have ASIs calibrated in M.P.H. We used to have one on the fleet at Wycombe. You had to be careful as all the others were calibrated in knots. On one occasion I forgot which plane I was in and flew the approach at 70 - 65 mph :O

Brooklands

[Tango Oscar]

I was taught to hold some back pressure and let the plane fly itself off the runway in a traumahawk. I found it quite difficult to know how much back pressure to apply, but eventually got the hang of it. On my GFT the examiner told me not to rotate until we had atleast 60kts, as we were heavy (two bigish blokes with full tanks) !!

I now fly a Robin, and actively rotate at the correct speed. For me, it works much better.

[big.al]

Attempt no. 2 at posting this, due to busy server.....

I fly a C172 from a long tarmac runway, and use the method of instructor 2 (except it's airspeed and not ground speed of course). A positive rotation gives the benefit that you can hold the a/c on the runway until the airspeed is well past the stall speed, although too enthusiastic a rotation could lift the nose too high and enter a stall, which is not advisable without airbags...;)
The POH will give the definitive speeds, based upon MTOW, although if the a/c is at or near MTOW I always add a few knots extra to the take off speed before rotating where the length of the runway is not an issue.

The instructor teaching method 1 may be trying to get you used to flying from short runways. Short-field technique (which of course differs depending upon a/c - always check the POH as FFF suggests) usually involves gradually increasing back pressure to get the a/c off the deck as early as possible. The downside is that when the a/c flies off the runway in this manner, it has only just reached flying speed. Therefore it is also very close to stall speed so care must be taken not to lift the nose too quickly and to allow the airspeed to increase before commencing a climb, otherwise those airbags will be needed again.

If you were using the soft-field technique you would probably try to unload the weight off the nosewheel as early as possible in the take off run to reduce drag from friction (wet grass, mud etc). Obviously not an issue from tarmac but if you are still learning, the instructor will try to familiarise you with different techniques for the conditions and the runway type/length. You won't always have the luxury of 1km or so of tarmac...

[StrateandLevel]

Rotation is designed to ensure that a Performance A aeroplane will achieve the screen height at the first obstacle following failure of the critical power unit at V1.

So its eminently suitable for a 172!

[Wee Weasley Welshman]

Positively rotate at the POH derived airspeed. That will work on long runways, short runways, grass runway, crosswind take offs, downwind take offs, flapless take offs, full flap take offs - you name it.

Cheers

WWW

[Circuit Basher]

Until I started flying the Fuji a couple of years back, I was probably more of the school that gently nudged the aircraft off the deck quite quickly (also, most of my flying was in a PA28 out of Bournemouth), accelerated in a level attitude in ground effect and then established a positive rate of climb. The only exception was if I was flying an aircraft with a nose wheel shimmy that I'd just take as much pressure of the nose U/C as possible without presenting too much of the draggy wing planform to the oncoming airflow.

These days in the Fuji, the stall warner is a tad on the premature side (but nosewheel shimmy can be noticeable and the prop is long compared to the ength of the nose leg), so I pull back a bit on the column but do not rotate until I can fly cleanly away from the ground without the stall warner going off.

[Gertrude the Wombat]

FFF:In my limited experience, I'd say the practice of letting the aircraft fly itself off the runway tends to apply to tail-draggers. And floatplanes.

[Flyin'Dutch']

MPH/KTS

US including 1976 and before MPH after that KTS.

Fly off or rotate, really depends on aircraft you fly and conditions, and to some extent personal preference.

In a crosswind you may want to have some overspeed before you liftoff to prevent settling with some drift.

FD

[MLS-12D]

Really it doesn't matter very much when you're dealing with most nosewheel airplanes; at least not easy-flying 'planes like the 172. The 172 was deliberately engineered to make pilot technique as unimportant as possible (the old Cessna adverts suggesting that "anyone can fly", and boasting about the airplane's 'land-o-matic' capability, were not all that far from the truth).

Although I am a 'tailwheel snob' (preferably with sticks, not steering wheels), the easy-fly features were not, and are not, necessarily a bad thing. The 172 is a boring airplane, but let's face it, it has the best safety record going.

[bookworm]

Instructor No.1 says, "on take off allow the speed to increase with gentle back pressure and the aircraft will fly itself off".

The problem with letting an aircraft "fly itself off" comes in crosswinds. The weight on the wheels, and thus any lateral grip of the tyres, gradually decreases to zero as speed increases to the "fly itself off" speed. The lateral grip may not be enough to keep you straight. A positive rotation can probably be achieved while there is still enough weight on the wheels to cope.

[rottenlungs]

Hi there

I am fairly early in my PPL training and therefore have little experience. however, I have flown with instructors who taught both methods. In the Tomahawk, I was told to take the weight off the nosewheel. In the 152 I now fly (god that wing blocks the view!) I accelerate to 55 and then positively rotate away, letting the speed build to 70ks in the climb.

For me, I have found the second method much more manageable. I found it hard in the Tomy taking the weight off the nosewheel without lifting off prematurely (stall warner bleating every time!).

Cheers

Lungs

[FlyingForFun]

Gertrude,In my limited experience, I'd say the practice of letting the aircraft fly itself off the runway tends to apply to tail-draggers.And floatplanesI don't know about that... but I hope to find out soon! (http://www.pprune.com/forums/showthread.php?s=&postid=1055702) :D ;)

As for cross-winds, I thought the idea was to apply full into-wind aileron at the start of the take-off roll, and gradually decrease the aileron as you gather speed and the controls become more effective. Thus, when the wheels loose their grip, the horizontal component of the lift vector should keep you going straight down the runway. Admittedly easier in a tail-dragger... which might be why they are more often flown this way???

FFF
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[Northern Highflyer]

I always keep the weight off the nose wheel on grass runways, partly for the drag, and partly for any bumps I always seem to find. There is one bumpy runway at my local field with a bump that always meets you before you reach the rotate speed, lifts you a little, then you settle back on the runway again. As it is a short runway with a mine at the end of it, this can be a little unsettling for any student/newly qualified PPL.

It's horses for courses.

[Tinstaafl]

It depends on what the a/c manual says, the circumstances & the characteristics of that particular a/c.

* It's generally accepted that reducing at least some of the load on the nosewheel is a 'good thing'.

* A rough or soft surface tends towards keeping as much weight as possible off the nosewheel, in which case the a/c will tend to 'fly off'.

* A strong x-wind tends towards holding it on then a positive rotation to get airborne with minimal time in the transition from wheel-borne to wing-borne. Some types are more amenable to being held on than others.

* What's the likely hood of severe turbulance/windshear immediately after take off? Additional energy in the form of height &/speed is useful in this case. Obviously height can't be stored but additional airspeed can by rotating later than usual. Admittedly this isn't a common situation for many although it is for me.... :ooh:

* Overlaying all the above is TODR vs TODA and any performance mandated technique to achieve this.






blody tipos

[Dude~]

You should try flying a Partenavia P68. On take off, you raise the nose quite considerably and then after a pause, it lifts off, I loved it because it felt like a mini airliner, especially with its doorless cockpit! Landing was similar - demanding a pronounced de-rotoate after touchdown.

I remeber flying it solo once with just a drop of fuel on board. The 400hp dagged me down the runway like a rocket, pulled the nose up, then it positively lept off the runway and climbed like a b**ch.

Far more satisfying than a vague soft field take off in an under-powered, over-loaded piper single!

[bookworm]

As for cross-winds, I thought the idea was to apply full into-wind aileron at the start of the take-off roll, and gradually decrease the aileron as you gather speed and the controls become more effective. Thus, when the wheels loose their grip, the horizontal component of the lift vector should keep you going straight down the runway.

The problem is that in order to get a horizontal component of lift, the aircraft has to be banked. That would mean rolling down the runway on the nose wheel plus one main wheel. If the crosswind is so strong that I have to bank before I'm airborne, I think I'd prefer to be on one wheel -- just the main. Come to think of it I think I'd prefer to be on the apron, waiting for better weather. :)