Arm Fatigue Before Trim Tabs
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Arm Fatigue Before Trim Tabs
Hi all,
Many years ago, my engineering lecturer told us a story of how pilots in WW1 always stood in a certain pose for photos after missions because their arms were fatigued and sore. Typically their arms were bent, as they could not straighten them. This was apparently due to a lack of trim tabs, which checks out given the invention of Flettner tabs was during WW1, so one would expect a lack of trimming in most WW1 planes and flights.
Is there any truth to this? Especially the part about the photos? Anyone recall any stories?
Cheers,
Many years ago, my engineering lecturer told us a story of how pilots in WW1 always stood in a certain pose for photos after missions because their arms were fatigued and sore. Typically their arms were bent, as they could not straighten them. This was apparently due to a lack of trim tabs, which checks out given the invention of Flettner tabs was during WW1, so one would expect a lack of trimming in most WW1 planes and flights.
Is there any truth to this? Especially the part about the photos? Anyone recall any stories?
Cheers,
I own and operate a new aircraft with no trim tabs. No arm fatigue issue because the entire horizontal stab is moved for pitch trim. You will find that many aircraft, gliders, small single engine, and large transport, do not use trim tabs. They do all have some means of trimmmg out the pitch control forces though and I don't know if/when this was introduced in WW1 aircraft.
This thread says several WW1 aircraft had pitch trim. - https://bbs.hitechcreations.com/smf/...opic=283906.15
This thread says several WW1 aircraft had pitch trim. - https://bbs.hitechcreations.com/smf/...opic=283906.15
I own and operate a new aircraft with no trim tabs. No arm fatigue issue because the entire horizontal stab is moved for pitch trim. You will find that many aircraft, gliders, small single engine, and large transport, do not use trim tabs. They do all have some means of trimmmg out the pitch control forces though and I don't know if/when this was introduced in WW1 aircraft.
This thread says several WW1 aircraft had pitch trim. - https://bbs.hitechcreations.com/smf/...opic=283906.15
This thread says several WW1 aircraft had pitch trim. - https://bbs.hitechcreations.com/smf/...opic=283906.15
Some WW1 aircraft may have had pitch trim, but some (most?) didn't.
If I remember correctly, some gliders I flew had a spring connected to the yoke. You turned the spring tighter or les, to eliminate the steering force. There was no trim tab on those old gliders
See here:
DSC_2726_resize by Jelle Hieminga, on Flickr
This is typical of the Fokkers that flew in WWI, a horizontal stabiliser that was fixed to the fuselage structure and a set of elevators without a trim tab to be seen. You would have to go through some photos of other types, but it would not surprise me if there are plenty of examples that show a similar setup.
Have a look at this discussion: TRIM (or lack of it) [Archive] - The Aerodrome Forum
The short summary is that some types (SE.5 and Sopwiths are mentioned) did have a trimming device, but most German and French types did not. A lot of them had some sort of ground adjustment though. Keep in mind that the speed range for these types was pretty limited, and as elevator trim is mostly needed to cope with different speeds, the real necessity emerged when typical climb, cruise and descent speeds started to diverge after WWI.
This is typical of the Fokkers that flew in WWI, a horizontal stabiliser that was fixed to the fuselage structure and a set of elevators without a trim tab to be seen. You would have to go through some photos of other types, but it would not surprise me if there are plenty of examples that show a similar setup.
Have a look at this discussion: TRIM (or lack of it) [Archive] - The Aerodrome Forum
The short summary is that some types (SE.5 and Sopwiths are mentioned) did have a trimming device, but most German and French types did not. A lot of them had some sort of ground adjustment though. Keep in mind that the speed range for these types was pretty limited, and as elevator trim is mostly needed to cope with different speeds, the real necessity emerged when typical climb, cruise and descent speeds started to diverge after WWI.
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I design and fly R/C model aircraft. The transmitter has a trim facility, which alters the neutral position of each channel. However, I know that with careful design I can set a model up so that trimming is rarely needed. Some down thrust on the engine minimises the pitch trim changes caused by throttle operation, and some side thrust minimises the yaw . I know from experience what angles to build in at the design stages, and fine tuning after the first flight is achieved with shims added to the motor mount.
I end up with a model which once set up, will climb with full power, fly level at half throttle, and descend with idle power, all without using the trims, Constant speed, variable noise.
I imagine the early aircraft were set up in a similar manner.
I end up with a model which once set up, will climb with full power, fly level at half throttle, and descend with idle power, all without using the trims, Constant speed, variable noise.
I imagine the early aircraft were set up in a similar manner.
The thread I linked to above mentions this practice as well, someone states that some Fokker types were built with a bit of fin offset and a slight angle on the engine. Apparently on one British type there was an option to adjust the incidence on one mainplane. All so it would fly at a certain speed/attitude combination without too much needed input. You would still need a continuous pitch input for any other speed/attitude combination but it was mentioned that having the airframe set up for a continuous climb, it would alleviate most of the pitch forces for a longish part of the flight.
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I've read that when Alcock & Brown flew the Atlantic, they took with them a large piece of elastic to help ease the control loads - but it proved too short.
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Thanks everyone! Very interesting! Yes sorry I did mean the ability to trim at all - which I assumed to be mostly a consequence of a trim tab that could be adjusted in flight as the CoG changed.
It does seem like the there is much more to the history than I was lead to believe.
It does seem like the there is much more to the history than I was lead to believe.
I agree, they are both a delight to fly. The K6-CR as that had a conventional fixed tailplane and elevators (and trim tab?). The K6e (and the SF-27) had an all moving tail of symmetrical section pivoting around 1/4 chord so there was no stick force at all but for the spring. The effect was that the trim curve was identical at all speeds so care was needed when pitching at high speed.
From "Flying the Atlantic in Sixteen Hours" (Brown, 1920):
No trim controls to be found... unless I missed them (this is the reproduction Vimy of course):
At no time during the past sixteen hours had the pilot's hands and feet left the controls. This was a difficult achievement for such a long period, especially as a rubber device, fitted to ease the strain, proved to be valueless. Elastic, linked to a turnbuckle, had been attached to the control lever and rudder bar; but in the hurry that preceded our departure from St. John's, the elastic was cut too short. All the weight of the controls, therefore, bore directly on the pilot.
