Trimming under 300 feet

[Rubber Dagger]

Hi all,

I would appreciate some feed back on what your thoughts are with regards to trimming under 300 feet, should you or should you not?. My reasons for this question are that on my CPL course my instructor insisted on trimming A.S.A.P after rotating, "why struggle when there is no need to" he said. But my local flying school teach the students not to trim untill above 300 feet. Your views please.

[IRRenewal]

Give me one good reason why you wouldn't trim below 300 feet.

Holding the throttle is not a good reason. That is why they invented throttle friction devices.

[nosehair]

Never heard of it. Do you mean trimming on take-off? How about on a go-around? That almost always requires trimming - and some airplanes can overcome the pilot if not trimmed. In my opinion, that is a dangerous thing to teach - not trimming.

[Flyin'Dutch']

Can't think of any good reason not to trim.

Are we talking trimming by hand or with an electric trim?

If you don't think that you need to trim for any new attitude feel free to have a go in the Maule. Set it up for the approach with full flaps and 70 mph and then do a go-around. You'll be reaching for that trimwheel PDQ!

:E

FD

[bookworm]

RD

Any chance that your local flying school flies Pipers like the early PA28s and PA30s? It's rumoured that Piper wanted to put the trim wheel in the baggage compartment to get it out of the pilot's way but there wasn't room so they put it on the roof instead. ;)

I can see an argument for not moving from throttle quadrant to roof mounted trim at critical moments, though I don't think it's necessarily correct.

[Rubber Dagger]

Thanks guys,

Its an interesting one this, i am talking trimming on take off, i always trim the stick forces A.S.A.P as one of the aircraft i fly (PA28 Arrow IV) needs alot of forward pressure to keep the nose at the correct attitude in the climb out, what if the seat ratchet where to brake sending the pilot backwards? at least if the pressures are trimmed out you may have a chance to recover! The club concerened have a varied fleet of aircraft, Grob's, C150's-152's-172's, and Warriors. Its interesting to get your views.

Cheers.

:ok:

[pilotbear]

ALWAYS ALWAYS fly the aeroplane in trim......no excuses at all:ok:

[Ex FSO GRIFFO]

G'day Bookworm,
'Tis GOOD to keep it trimmed....makes 'LIFE' easy.... ref the ol' PA28 etc with the roof mounted handle...a reasonable practice I used to teach was to wind the handle to the middle of the selected range for T/O, THEN, set it at the NEAREST "3 o'clock" position as viewed from your seat. Then, If ya want trim down, knock it forward and keep winding as req'd. If ya want it nose UP, hit it backwards and ditto. No thought req'd. And yep, the throttle friction works as advertised.
My 'handy hint for the day'.....Cheers.
Areq QNH 1013...:ok:

[mstram]

Rubber,

S.o.p. in any plane is to set the trim as part of the pre-takeoff procedures. True it might be a rather "coarse" trim, but after liftoff and climbing out, it should only take very minor trimming.

I can also see your instructors point. If the aircraft is trimmed reasonably for takeoff, "any mis-trimmed" forces should be very minor, and you can probably wait until past 300 agl, to "fine tune" them .

.. Although I don't know what significance he's placing on 300 agl anyway. A glider will be able to turn back to the rwy, but a light power plane is going to land pretty much straight ahead, maybe 20-30 deg left or right at most in the next 30 seconds or so !

Mike

[InTheAir]

Club instructor refused to let me trim before 500ft (PA-28) on touch and go's, never heard this from anybody before, not one of the 6 instructors I've flown with prior to that have ever asked me not to do it. Naturally I had to adopt the latest instructor 'preference' in order to get checked out, but rest assured one day some one will say.... "trim, damn it!" :{

[Flyin'Dutch']

ITA,

Next time you go and fly with that instructor can you ask him/her WHY?

May be it is something we don't know.

:E

FD

[InTheAir]

Actually I do vaguely remember the 'hand on throttle' excuse.

I find it funny how forcing someone to fight a yoke which is pulling forward with all it's might *with one arm* is preferred to no hand on throttle.

[hotprop]

I've never fully understood the reason for hands on throttle until cruise level or whatever it may be. In 470 hrs I've never had a throttle move unless i moved it, in most cases there's enough friction in the system.

So why all the fuss ?? Could someone enlighten me :hmm: ..

[Gertrude the Wombat]

So why all the fuss ?? Could someone enlighten me You've clearly been lucky enough not to fly ancient aircraft with a useless throttle friction system ... I've never actually had a throttle vibrate closed on me but that's why I was taught to do it.

[hotprop]

Nope, my oldest vintage aircraft experience is of the early 1960s. That's only 40 odd years, so there must be some older stuff out there in which power is significantly reduced by vibration to justify throttle grip in favour of trimmed aircraft.

Beats me ...

[susan burgess]

could this refer to the aircraft which use first stage of flaps until 300 feet.The aircraft which use flaps are only trimmed after the flaps are raised.

[IRRenewal]

The aircraft which use flaps are only trimmed after the flaps are raised. Why? If the aircraft is badly out of trim I would still trim, even if I knew I'd have to do it again in less than a minute.

Gertrude, would that be a Tiger Moth? If so, I do consider myself lucky not to fly them. Worst handling aircraft I have ever flown.

[hotprop]

That must be it.
Raising flaps requires removing your hand from the throttle (or stick perhaps) and giving the trim a spin at the same time should be feasible without too much powerloss.

I don't know what the standards are elsewhere but in Sweden most training flights level off at 1000-1500 feet initially after which cruise power and trim is set. Flying those few minutes with a rough trim setting should be OK, but for cruise climbs etc trimming must be approved I think - sounds rather ridiculous not to allow it.

An electric trim really helps and does away with the issue altogether.

[Gertrude the Wombat]

Gertrude, would that be a Tiger Moth? No, I just got the impression that if you didn't maintain your 152 or whatever properly then the rubber would go off after a few decades, and if you didn't replace it when necessary then the throttle friction wouldn't work as advertised. Of course the instructor who told me this was at pains to point out that their 152s got fixed when necessary, but that it was still a good idea to keep one's hand on the throttle against the day when one was flying some crappy aircraft rented from elsewhere. (Or, of course, against the day when one forgot to adjust it properly.)

In a 152, of course, one can adjust the trim without noticeably removing one's hand from the throttle anyway; I was certainly never taught to fly out of trim for more than a few seconds at any point[1], and I've been left with the habit of keeping in trim from wheels leaving the ground onwards.

[1] Except in a Super Cub on floats on final, that is. If you trim for final, then pulling the stick fully back once you're on the water isn't necessarily enough to stop the front of the floats digging in. So you're pushing forwards quite hard on final, feels very odd.

[hotprop]

Our SuperCub used to trim itself ! Out of trim that is. It was very annoying. One had to keep a hand on the trim or re-trim every few seconds.

Has nothing to do with the original question perhaps, but trimming is essential ... :=

[FJJP]

A more likely reason why trimming below 300ft is not taught [at least to the ab initio] is simply to keep the workload to a minimum. A new guy has enough to think about in the initial stages of takeoff and climb without him trying to remove a bit of control force.
As time and experience progresses, he will have the mental capacity to safely do more and more.

[DFC]

Trying to fly an out of trim aircraft increases workload significantly because every time that the pilot relaxes the force on the stick, the attitude changes. Thus most of their effort (both physical and mental) is taken up with simply keeping the required attitude.

A quick adjustment to the trim can remove the out of trim forces and thus reduce the workload!

Regards,

DFC

[Tinstaafl]

I taught to trim anytime the a/c was out of trim, except if a deliberate untrimmed state was desirable eg turns or, for some types/pilot combinations, a slight nose up trim on short final.

I know I trim within seconds of the wheels leaving the ground if it's not correct. I also do so on approach up to the point where I commence the flare, if necessary eg flying a reducing speed profile. As far as I can see, altitude is irrelevent. The major factors are task priority & pilot capacity to attend.

[green dinosaur]

You should have your hand on the throttle during the climb out!! The throttle friction is ok, however some throttles still slide back, and its quite hard to detect. Also your aeroplane should be trimmed on the ground anyway during the pre-take off checks, to ensure that there isnt too much force on the controls during the climb out.

[DFC]

Green Dinosaur,

IMHO, the main reason for keeping one's hand on the throttle is so that one can close it asap if necessary during the take-off.

During the climb it is true that a worn friction lock can result in the power reducing. However, unless you have fabulous noise cancelling headset equipment, any significant reduction is highlighted by a change in sound when flying an aircraft with fixed pitch prop.

If one was to teach no trimming below 300ft then would also have to teach that the gear should not be retracted below that height despite what effect that can have on performance. After all, it takes about the same time to move the gear leaver through a few centimetres as it does to move the trim wheel by the same or less.

Yes the aircraft trim should be set to the take-off position before take-off. However you may have noticed that while aircraft like the C172 have a single position for take-off trim, the loading can vary by more than a bit. If you don't believe me, ask your back seat pax to lean forward for a minute and see what that does to the trim setting during the cruise.

Thus unless that POH gives a specific setting for every position of the C of G, there is probably going to be some trim adjustment required shortly after take-off and more so if the C of G is near any of the extremes!

Regards,

DFC

[BraceBrace]

Is he an airline pilot? Maybe he copied some procedures: no trim until gear up (the reason would be to prevent trim runaway with the gear hanging out on jets).

But still, I hate it if the aircraft is nose heavy in the climb and it requires forces to keep the nose up... trim it. Even on landing, on some Pipers (Archer/Seneca), we give 2 "bursts" up short final, while maintaining some forward pressure to keep it's attitude, then releasing it in the flare, which makes it a lot easier to land (especially on the Seneca this is really helpfull).

[fireflybob]

>Is he an airline pilot? Maybe he copied some procedures: no trim until gear up (the reason would be to prevent trim runaway with the gear hanging out on jets).<

Done the airline pilot bit for circa 25 years on Boeing and Airbus and never heard of such a procedure!

[green dinosaur]

A student with only 10 hours isnt going to be able to tell by the engine sound whether he's climbing at full power or only has 2200 rpm set, unless his hand is on the throttle.

Remember you are teaching students,not 500+ hour pilots here. Further, you can set the trim a little either side of neutral to take into account of pax size. Seems sensible to me!!

[BraceBrace]

@fireflybob: it must've been the first thing I heard in a jet sim, but it was with the airline that had one of the first stab trim runaway on takeoff accidents as well...:ooh:

[DFC]

green dinosaur,

I would hope that your 10 hour student would have an instructor sitting beside them who would calmly ask them if they think the engine noise has reduced slightly. If the student states that they have noticed the change in engine note then the instructor can calmly point to the fact that the attitude, and speed relationship are not what is normally expected and then perhaps the student might think that if the attitude is OK then the speed is low because the power is too low and pushing the throttle forward might help.

Which is more dangerous in your book?;

1. A pilot who makes a guess at where the trim should be set and places it somewhere other than the position recomended in the POH and then struggles with an out of trim aircraft until well above the surface ( but at a lower than normal speed due to an incorrect trim setting)? or;

2. A pilot who sets the trim as per the POH and then struggles with an out of trim aircraft until well above the surface ( but at a lower than normal speed due to an incorrect trim setting)? or;

3. A pilot who sets the trim as per the POH and then once airborne, uses the correct technique to keep the aircraft in trim at all times during flight?

To adjust the trim takes seconds.

The problem I have with all these AGL heights given to some students these days is that when departing from an unfamiliar field using QNH, they never work out what the appropriate altitude is for these restrictions.

How many students and PPLs are told - no flap retraction below 300ft and no turn until 500ft and depart from a 200ft elevation field and retract the flap at 100ft agl and turn at 300ft agl? Answer......lots

The great gotch ya for PPL checks is to ask them to climb at the best angle speed all the way to 500ft in an aircraft that uses flap for that. Almost 100% of them will automatically retract the flap at 300ft regardless of what the speed is!!

How many light aircraft descend while the flap is being retracted?

Would it not be better to say no turns at a speed below XX and don't retract the flap until clear of obstacles and the speed is above XX

Regards,

DFC

[Tinstaafl]

No difference between taking your hand off the throttle for a few seconds to adjust the trim than doing the same to raise the gear or raise the flaps or select/deselect carby heat or use a handmike (remember them?) or adjust the sunvisor or adjust a volume or set a heading bug or OBS etc etc etc ad nauseum.

[nosehair]

Two (2) very good reasons for keeping the hand on the throttle during T.O. & Climb-Out:
1) Throttles do creep out. Rare, but it does happen.
2) Training. Remember the Law of Primacy? Later, when you are flying Multi-Engine, the hand must be on the throttles to quickly snatch them back in case one fails on the T.O. roll, or after lift-off, and landing runway is still available in front. The hand must be on the throttles to effect a quick abort. If you don't do this in primary training, it will take a lifetime to instill at alater date.

But, the hand can move swiftly and purposefully to the trim control for a couple of seconds, then swiftly back to the throttle.

[chicken6]

Rubber Dagger

I think your question contains all the key words, you were training for your CPL and your local school was teaching students (as they do). Each to his or her own level.

IMHO there's no point fighting it, and a certain height AGL doesn't really matter. If you've got a higher priority (like controlling direction in twins and feathering the dead engine), then deal to that, but if everything's tickety-boo then why not make it REALLY easy?

Also, sometimes it's easier overall to not trim fully. For example, in bigger twins that can, on one engine, actually accelerate at acceleration altitude (all alliteration) it's easier in the overall scenario of EFATO to initially leave a bit of back pressure on the C/C so that when it accelerates by 10-20kts, it naturally tends to pitch up/reduce back pressure required, all meaning you don't have to retrim. This makes it easier to fly whatever the procedure is while mentally going through the problem, memory items, ATC, QRH, etc.

My two cents,

1. Do what your instructor says, with the caveat dont' do nuthin dumb. If your instructor tells you something different to someone else at the same organisation ASK WHY. Someone's not standardised. Go to the Chief if you have to, it's their playground.

2. If it makes life easier, do it. When it gets hard it gets really hard, really quickly, and you need all the cards stacked in your favour.

Enjoy
C6

[kookabat]

My instructor once asked me, at about 300' after takeoff, to 'check your trim'... naturally (despite the aircraft being trimmed pretty well) I took my hand off the throttle... which he promptly closed saying 'engine failure!' :\ - later he confessed that it was just a ruse to get my hand off the throttle so he could close it... b@stard! :}

Adam

[Chuck Ellsworth]

an aircraft properly trimmed will fly its self.

Nuff said?