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!



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.

[pilotbear]

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

[Ex FSO GRIFFO]

Trimming At 300 Feet

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...

[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.



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 ..

[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 ...