ajaaron
Posts: 136
Joined: Thu Nov 02, 2000 9:31 am

Will I Ever See The Tailplane Trim?

Fri Dec 14, 2001 10:04 am

If I want to see the stab trim move (i.e. with binoculars as a spotter) when will it occur on say a 747/777/757?

Before pushback?

After hydraulics are on following after engine startup?

On taxy, as the Before t/o checklist is completed?

Thanks, cos I've never seen them move when I'm spotting planes taxying for t/o with binoculars at Heathrow.

However, when I was a passenger on an L10-11, seated at the back on final approach I saw the tailplane move as the pilot trimmed - and boy did it move - fast and pretty substantial movement!

 
drgreen757
Posts: 144
Joined: Sat Sep 15, 2001 1:50 am

RE: Will I Ever See The Tailplane Trim?

Fri Dec 14, 2001 11:31 am

Most horizontal stab's are already set before you even get on the aircraft, and stay there all the way thru engine start and takeoff. Boeing 757 stab trim is usually set to 4 units of trim. And when it is moved, it will usually be small minute movements that would be hard to see anyway, especially with binoculars.

As for the L-1011, it has an all moving horizontal stab. When the pilots pull and push on the control yoke, the entire Stab moves. The entire surface serves as the elevators, and what would normally be the elevators are trim tabs that can be adjusted up and down.

I hope this helps you out some!

Scott
Save the grey ghosts.
 
L-188
Posts: 29881
Joined: Wed Jul 07, 1999 11:27 am

RE: Will I Ever See The Tailplane Trim?

Fri Dec 14, 2001 11:41 am

I have seen them move plenty of times. Look for it right before and after an aircraft get de-iced.

Some aircraft makers require that the tailplane be set at a certian angle to allow for any fluid to drain from in and not get trapped in components.

If memory serves in the 727-100 it was full Nose Up trim. Correct me if I am wrong.

If you have a freind that has a Super Cub they trim the same way. Just have him jump in the cockpit and crank it through a couple of times.
OBAMA-WORST PRESIDENT EVER....Even SKOORB would be better.
 
Minuteman
Posts: 260
Joined: Sat Aug 05, 2000 1:01 am

RE: Will I Ever See The Tailplane Trim?

Fri Dec 14, 2001 1:15 pm

You're probably not going to see any appreciable movement.

In a typical situation, a horizontal stabilizer is going to trim from around 13 degrees deflected nose up to 2 or 3 degrees nose up alignment with the fuselage (usually, not sure what that works out to in Trim Units). The trimming will occur over the entire climb, so you're talking about a ten degree change in deflection over twenty or thirty minutes.
 
AJ
Posts: 2295
Joined: Wed Nov 03, 1999 3:54 pm

RE: Will I Ever See The Tailplane Trim?

Fri Dec 14, 2001 1:28 pm

On our 747-400s the trim is set on receipt of the loadsheet, so very close to pushback.
 
Metwrench
Posts: 715
Joined: Fri Aug 17, 2001 11:25 am

RE: Will I Ever See The Tailplane Trim?

Fri Dec 14, 2001 1:33 pm

The only time you are going to see a lot of horizontal stabilizer trim movement is on the Flight Crew's preflight before the first flight of the day. Or possibly during a Maintenance Check.

High-speed film of an A/C landing will catch it but movement is still subtle during flight.

It's a big suface, doesn't need to move a lot to have a big impact.
 
Twotterwrench
Posts: 1087
Joined: Tue Jan 16, 2001 5:57 pm

RE: Will I Ever See The Tailplane Trim?

Fri Dec 14, 2001 2:45 pm

Stop by the hangar tomorrow. I'll let you move it all yo want...  Smile/happy/getting dizzy
 
timz
Posts: 6160
Joined: Fri Sep 17, 1999 7:43 am

RE: Will I Ever See The Tailplane Trim?

Sat Dec 15, 2001 7:33 am

As for seeing the tailplane move, dunno. But on the IL-62 the result (the difference between the tailplane's position on arrival at the gate and on departure from the gate) was certainly obvious.

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