Simviation Forum - trimming the default 737-800

Dec 12^th, 2010 at 9:02am

DenisH Offline
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After a year of flying smaller single and twin engine aircraft I'm now moving up to the larger jets. The default Boeing 737-800 for starters. However, I find manually keeping trim on this airplane almost impossible. Can it be a bug or is trimming larger aircraft best left to the auto pilot?

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Reply #1 - Dec 12^th, 2010 at 10:39am

olderndirt Offline
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DenisH wrote on Dec 12^th, 2010 at 9:02am:

After a year of flying smaller single and twin engine aircraft I'm now moving up to the larger jets. The default Boeing 737-800 for starters. However, I find manually keeping trim on this airplane almost impossible. Can it be a bug or is trimming larger aircraft best left to the auto pilot?

Dennis - are you hand flying this beast or using auto pilot?

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Reply #2 - Dec 12^th, 2010 at 12:16pm

DenisH Offline
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OLD: Hand. Can't keep it level with manual trim more than a minute or two. Then it seesaws.

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Reply #3 - Dec 12^th, 2010 at 8:53pm

olderndirt Offline
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DenisH wrote on Dec 12^th, 2010 at 12:16pm:

OLD: Hand. Can't keep it level with manual trim more than a minute or two. Then it seesaws.

I don't know the MS secret to FS trim - doesn't appear to have anything to do with aerodymic pressures or any of that. You spend a lot of time chasing the nose but, without the feel of airflow and pressure on the controls, I think we're stuck

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Reply #4 - Dec 12^th, 2010 at 9:57pm

DenisH Offline
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Yep! But still a marvelous hobby for us men of a certain age. . Better than searching for nickles and dimes under now-outlawed playground monkey bars with a metal detector.

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Reply #5 - Dec 13^th, 2010 at 9:56am

RitterKreuz Offline
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One thing i would like to add to the discussion is the length of airliners makes the aircraft one big seesaw.

let me provide a real life example.

You constantly have people getting up and going to the lavatory, flight attendants constantly walking up and down the aisle with their service carts etc, even fuel burn - these all change center of gravity constantly, even if only slightly.

with the autopilot on, if you had the opportunity to sit in the flight deck as i have and feel trim wheels against your leg or see them from the jump seat etc - generally they are constantly moving - re-trimming the aircraft - only if a little at a time.

it would be a full time job to hand fly an airplane such as a 737 or 747 etc in cruise flight from point A to point B

generally the practice is to hand fly the aircraft to an initial altitude about 2-3,000 ft above ground and then activate the autopilot which has been pre-set while on the ground to desired variables such as speed, altitude and heading etc.

as changes need to be made to heading or altitude - then the desired altitude or heading is selected and the system takes care of the rest.

for the most part, in the airline environment you are a "systems manager" more than you are an "aviator", with "hand flying" accounting for probably 10-15% of an actual flight.

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Reply #6 - Dec 13^th, 2010 at 11:14am

DenisH Offline
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RITTER Many thanks for your very lucid explanation. Your comment re systems management is interesting and makes me wonder why flying the big jets is so popular in flight simming.

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Reply #7 - Dec 13^th, 2010 at 6:35pm

reachva Offline
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as Ritter pointed out, in modern airliners you spend very little time actually flying the plane and more time watching the systems in case of failures. Its well known that modern aircraft could fly themselves completely without the needs for a pilot at all but its not done as passengers wouldn't feel safe trusting their lives to a few computers.

If you want some hands-on flying, the piston pounders are for you Wink

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Reply #8 - Dec 13^th, 2010 at 10:41pm

DenisH Offline
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Yep. I wonder how the early jet airliners were flown? Half & half? I flew on a BOAC jet flight years back but can't recall the aircraft model (if I ever knew it). This was during the time when prop airliners were being phased out on major routes. I was spooked (as usual) because BOAC's safety record was suspect at the time. Or maybe it was the aircraft's record. I forget which.

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Reply #9 - Dec 14^th, 2010 at 2:53am

Hagar Offline
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DenisH wrote on Dec 13^th, 2010 at 10:41pm:

Yep. I wonder how the early jet airliners were flown? Half & half? I flew on a BOAC jet flight years back but can't recall the aircraft model (if I ever knew it). This was during the time when prop airliners were being phased out on major routes. I was spooked (as usual) because BOAC's safety record was suspect at the time. Or maybe it was the aircraft's record. I forget which.

I suspect it was the Stratocruiser. The engines weren't too reliable. None too popular in some quarters including the legendary chief pilot of BOAC. http://b377.ovi.ch/articles/speedbird/

Edit. Oops! Just noticed it was a jet. Probably the Comet. http://en.wikipedia.org/wiki/De_Havilland_Comet#Comet_disasters_of_1954

« Last Edit: Dec 14^th, 2010 at 4:22am by Hagar »

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Reply #10 - Dec 14^th, 2010 at 10:26am

DenisH Offline
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Hagar: Yes, you're correct. It was the Comet.

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Reply #11 - Dec 14^th, 2010 at 10:32am

olderndirt Offline
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Even with the smallest personal aircraft, you can spend a fair amount of time adjusting trim tabs so that, in smooth air, that baby will fly hands off. Usually pitch is easiest but yaw becomes problematic if the wings are out of rig. Ideally, when all tabs are bent just right and God is in his heaven, you can hit the cruise control, lean back and admire your panel - that's how the big boys do it - sort of

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