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Questions about "Takeoff Trim" and "Auto Brake" (Read 2156 times)

May 3^rd, 2004 at 4:36pm

GeneticA Offline
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Hello,

I have a couple of questions, I would be more than happy if you help me with these.

1- I always hear about take off trim setting. In the aircraft manuals this is written as "Trim - Takeoff Setting". I guess it is a bit nose-up trim, but how much? What will it be for a Cessna 172 or for a 737?

2- There is a Auto Brake selector in boeings. It can be set to OFF, RTO, 1, 2, 3. What are this for? Does this apply brakes on gears or is it some kind of an air brake? And what should this be set at t/o, approach, landing,and descent?

Thanks in advance.

I'm trying to land&&This aeroplane of ours gracefully&&But it seems just destined to crash&&(Björk - So Broken)

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Reply #1 - May 3^rd, 2004 at 4:56pm

Dan Offline
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Hi mate, Will help with q2. It means Rejected Take off, and 3 different strengths. On T/o, just be ready to hit RTO if summat goes wrong. Then during cruise, set it to the required strength for your runway lenght, around 3 for a 777 and 7000ft of tarmac. And its wheel brakes.
Dan Wink

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Reply #2 - May 3^rd, 2004 at 6:41pm

Nexus Offline
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Take off trim setting is very important, and is not a constant value. Depending of CG (center of gravity) and flap setting. When CG and flap setting is entered into the FMC take off page, the computer will calculate take off trim for you (Gross weight must have been entered in the Performance Initialization page)

This field is complicated (as aviation in general) but you'll get takeoff warnings if trim is below 2.40 and above 8,75

For flightsim, use around 5 - 5.0, that should be okay

The 737 horizontal stabilizer can move 17 units.
Horizontal Stabilizer leading edge up 4,2 degrees (nose down)
Horizontal Stabilizer leading edge down 12.8 degrees (nose up)
The data above is with the Next Generation 737's but I think numbers are the same for the earlier models aswell.

Regarding the RTO...
The mode is armed when speed is greater than 90kts
Activated (ie spoilers extended) if speed greater than 90kts and you retard the throttles to idle.
1-3, and MAX is the strength where MAX is hardest braking action.

The 767, for an example has a wider selection, RTO, DISARM, 1, 2, 3, 4, MAX AUTO and OFF. Max. manual braking is always stronger than max. autobrakes 8)

Hope this helps!

« Last Edit: May 3^rd, 2004 at 9:39pm by Nexus »

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Reply #3 - May 4^th, 2004 at 1:01am

GeneticA Offline
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Thank you very much Dan & Nexus82

I'm trying to land&&This aeroplane of ours gracefully&&But it seems just destined to crash&&(Björk - So Broken)

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Reply #4 - May 6^th, 2004 at 2:52pm

Dan Offline
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Your are very welcome!
dan

&&3DMark01 || OCUK - The best UK shop

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Reply #5 - Jun 22^nd, 2004 at 11:46am

Skittles Offline
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Quote:

..."Trim - Takeoff Setting"... What will it be for a Cessna 172...

On the main 2D panel of the 172 there is a T/O pointer, set the trim marker there.

What do computers and air conditioners have in common?
They both will work perfectly, until you open windows.

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Reply #6 - Dec 16^th, 2004 at 11:38pm

N556EP Offline
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Funny enought i just read an Article on braking. the promblem now a days is carbon brakes, PIlots think that if they use them too much during taxi it will diminsh them but in reality the oppsite is true. Carbon brakes operate well under high temps, which you can use them more during taxi or on roll out. Now im not sure what aircraft uses Carbon brakes but im sure Cleveland sells Upgrades lol. Anywase now pilots reley on thrust reversers to stop. Now Thrust resvers are an added thing, but put more starin on the engine, they say pilots should rely on Auto brake if Equipped, becuase the sytem can be more exact than the pilot when used wth thurst resvers Braking is a touchy subject in Aviation.

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Reply #7 - Dec 17^th, 2004 at 6:50am

jrpilot Offline
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Quote:

Anywase now pilots reley on thrust reversers to stop. Now Thrust resvers are an added thing, but put more starin on the engine, they say pilots should rely on Auto brake if Equipped, becuase the sytem can be more exact than the pilot when used wth thurst resvers Braking is a touchy subject in Aviation.

When I land the 737NG sometimes I forget to put those autobrakes down and when I land with just reverseyou can surly feel hwo much of a diffrence you need

And to give some more info...on a normal landing a pilot usualy goes to manually braking below 80kts???...correct Nexus?

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Reply #8 - Dec 20^th, 2004 at 10:00am

beefhole Offline
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In real life, the trim setting for a 172 on t/o is neutral, right on the white line(in fs, I actually think the white line marker isn't neutral, but whatever). However, in fs, you don't get the same forces pulling back on your joystick like in real life so I'd recommend trimming it up before t/o.

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Reply #9 - Dec 28^th, 2004 at 11:23pm

Rocket_Bird Offline
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Trim settings depend on your aircraft really. I don't know too too much about the 172 or 737, but i think 172 is about neutral, 737 .

Now the auto brake selector. That I know something about. Generally the autobrake is controlled by a black box that automatically applies your brakes at a pressure depending on the amount of skid. RTO is for rejected take off, if you drop power after a certain airspeed, your brakes will engage until your plane is at a screeching halt! Setting 1 is for a standard dry runway. 2 and 3 are for slightly worst runways, rain and snow i think... lets your gear skid a bit more. I cant remember for sure.

Cheers,
RB

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Reply #10 - Jan 16^th, 2005 at 11:28pm

flightmedic Ex Member

I am a 172 pilot and unless you are leaving a soft or short field, there is NO trim or flaps used for take-off. Even when landing (under normal circumstances - no soft or short field) You use only 10* flaps. If you think because the plane is heavier you use more flaps or trim, then you havn't done a full flight plan with CofG filled out or takeoff and landing distances with pressure altitude corrected. IT MAY WORK IN A SIM BUT IT DON'T "FLY" LITERALLY IN REAL LIFE. Unfortunatley in real life you can't restart, if you don't do the figures properly.........you get hurt or worse yet....buy the farm.

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Reply #11 - Jan 16^th, 2005 at 11:38pm

beefhole Offline
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Hmm, interesting flightmedic. I, too am a 172 pilot (ok, with 11.5 hours I'm a wannabe, but you get the point) and I have been taught to always, always land with 30 degrees flaps. While my home field could be considered short-field, the runways at northeast philly definitely are not considered to be short-field landings and we still use 30 flaps. I'm confused now.

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Reply #12 - Jan 17^th, 2005 at 12:08am

Brute Offline
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In different areas different slang is used, in different pilots different procedures are used tom*ato toma*to

Future pilot...so you can scream to god, he cant hear you

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Reply #13 - Jan 17^th, 2005 at 11:07am

beefhole Offline
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I know, but 10 flaps is 10 flaps, no matter where ya go Wink

Wink

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Reply #14 - Jan 18^th, 2005 at 1:46am

flightmedic Ex Member

hmmm...that is very interesting there Beefhole.

I have 47.6 hrs on the 172 and that is how I was taught. I have yet to use more than 10* flap for landing.(reg surface and conditions only---soft field and short field are diff---then I do use 30 flap)
Doesn't mean that is right or wrong though. Everyone is taught differently. I find it interesting to know how others are taught.
The first thing I learned after getting shot at in Yugo for the first time was" If your way is the only way......don't stand next to me cause I don't want die anytime soon"
There is always more than 1 way to skin a cat.
Don't be confused though,
ALWAYS, ALWAYS, follow your FI's intruction. Once you get on your own...then...you can find your "own" flavour.

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