Max Q wrote:
The Jetstar is an interesting aircraft with some unique design features
One of which is the stabilizer trim system, in a conventional set up in the horizontal stabilizer is attached to the rear fuselage and pivots nose up and down.
On the Jetstar the horizontal stabilizer is part of the vertical stab and is not adjustable(although the attached elevators are)
Instead the entire vertical tail ‘tilts’
forward or back, in turn changing the angle of the horizontal stabilizer
One of the Jetstar engineers subsequently went to work for Mooney light aircraft and incorporated the same feature in their single engine aircraft line
It is still being used to this day
If you look closely at photographs of the Jetstar you can see an exposed section of
highly polished aluminum at the base of the
vertical fin’s leading edge
This shows the range of movement utilized
for fore and aft trim
There are only 2 aircraft that use this type of pitch trim system, the single engine piston Mooney’s and the Lockheed JetStar.
But actually it was the other way around, Al Mooney after he left the company he helped found, Mooney Aircraft he then went to work for Kelly Johnson’s skunk works at Lockheed. He was tasked with engineering the design for the empennage section of the JetStar so he incorporated the same design he used for his Mooney airplanes. Since Kelly Johnson was the chief engineer of the JetStar I guess he liked the design because he approved it.
I cursed Al Mooney many times, probably each time I had to service the pitch trim servo unit, once every 200 hours to check the oil level, drain any water that would leak down the jack screws and grease the mechanism. The pitch trim unit had 2 motors, one main and a standby attached to a gear box with 2 large jack screws that moved the forward edge of the vertical stabilizer up or down. To access this pitch trim unit you had to crawl through an opening about 14 inches by 12 inches and place you body between all the control cables, making sure you do not put any weight on the 2” diameter fuel jettison line and then remove the cover plates to gain access to the pitch trim mechanism. I usually brought in my coffee with me because once I was in there I stayed until I finished the job so I did not have to go through all the contortions required to get comfortable again. It took about an hour and a half to do the servicing, changing a pitch trim motor took another hour or so.