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elevator /pitch control
There was a story in S&G some years ago about a ASW 20 sucessfully landed
without damage by use of flap changes; the pilot had read the manual. Following the fatal crash of a Cessna 150/150 hp two plane, due to a burned throughj elevator cable, two of us tow pilots experimented with pitch trim on the Citabria. WE concluded that a good landing is possible (one that you walk away from) with use of trim and power. No we did not try a landing. Here is a reason for buying a ship with aerodynamic trim, not just a spring on the stick. John Firth, Ottawa |
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I was told that Eric Hamill when he was on the staff of the London Club,
Dunstable once did a complete circuit in a 150hp Super Cub without touching the stick, to see if he could. Done of course on throttle, flaps, trim and rudder. He was very, very current at the time. I also heard that a Booker pilot of a 180hp Super Cub found himself with no elevator control because of a failure in the elevator circuit, and got it down safely. Long live the aerodynamic trim! W.J. (Bill) Dean (U.K.). Remove "ic" to reply. "John Firth" wrote in message ... There was a story in S&G some years ago about a ASW 20 successfully landed without damage by use of flap changes; the pilot had read the manual. Following the fatal crash of a Cessna 150/150 hp two plane, due to a burned through elevator cable, two of us tow pilots experimented with pitch trim on the Citabria. We concluded that a good landing is possible (one that you walk away from) with use of trim and power. No we did not try a landing. Here is a reason for buying a ship with aerodynamic trim, not just a spring on the stick. John Firth, Ottawa |
#3
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"John Firth" wrote in message ... There was a story in S&G some years ago about a ASW 20 sucessfully landed without damage by use of flap changes; the pilot had read the manual. Following the fatal crash of a Cessna 150/150 hp two plane, due to a burned throughj elevator cable, two of us tow pilots experimented with pitch trim on the Citabria. WE concluded that a good landing is possible (one that you walk away from) with use of trim and power. No we did not try a landing. Here is a reason for buying a ship with aerodynamic trim, not just a spring on the stick. John Firth, Ottawa Here's a story related to me by a jump pilot at a skydiver school. The aircraft of choice in those days was a Howard DGA (Damn Good Airplane), a single engine cabin monoplane powered by a Pratt & Whitney R-985 of 450 HP. It was never an easy airplane to land even under the best circumstances. As the pilot approached the drop zone he slowed the aircraft in preparation of the exit of 5 skydivers, he felt a tap on his boot and the control wheel came out of the panel - the bolt holding the control wheel tube had fallen out. As he looked at the detached control wheel in his hands, the jumpers looked too - and made a hasty exit. Alone in the airplane, he re-inserted the wheel into the hole in the panel. As he did so he felt the nested tubes catch at the burrs around the bolt hole where the missing bolt had been. As long as he was gentle with the elevators and ailerons, the friction held and he had control of the airplane. He flew around for an hour practicing gentle flying techniques and burning off some fuel. The owner of the jump school and the Howard was on the radio telling the pilot to just aim the old crate at an empty field and bail out. The pilot had never been too keen on parachutes despite his job so he insisted on a landing attempt. Using the elevator trim for pitch control and limiting the wheel inputs he lined up with the dirt runway. The trim proved inadequate for a full stall landing and the DGA bounced badly collapsed the gear and bending the propeller - but he walked away. The Howard was re-built and returned to service. Bill Daniels Bill Daniels |
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#5
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Andreas Maurer wrote:
On 4 Nov 2003 16:49:14 GMT, (John Firth) wrote: Here is a reason for buying a ship with aerodynamic trim, not just a spring on the stick. This is the cause why an elevator trim tab is required according to JAR 23, by the way - it's a safe backup control. But aerodynamic trim is bad in term of aerodynamic efficiency, I think this is the reason why all modern gliders have a spring trim. Should we always degrade the performance for a case taht should never happen. An exeception to this bad efficiency is the system I have seen on Robin airplanes, i.e. a balanced all moving elevator (hinge at neutral point) with a servo (anti)tab adjusted by the trim. The drawback of this system is that the force needed to move the elevator from the trimmed position becomes huge when speed increases. |
#6
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In article ,
W.J. \(Bill\) Dean \(U.K.\). wrote: I was told that Eric Hamill when he was on the staff of the London Club, Dunstable once did a complete circuit in a 150hp Super Cub without touching the stick, to see if he could. Done of course on throttle, flaps, trim and rudder. He was very, very current at the time. I read about some wiring getting stuck in a 172 elevator control and the CFI flying it to landing, so I experimented with throttle, flaps, trim, and rudder only landings. After three 172 flights, I and another CFI could land without touching the elevator. A few more flights and we could take off AND land without ever touching the yoke or trim. The next flight we did it without moving the seat either (weight shift for trim). Finally we were able to takeoff and land without moving the seat, without yoke, trim, or flaps (only using the throttle for oscillation dampening, and the rudder for turns). It was scary: we'd over-rotate on takeoff and have to reduce throttle to keep the stall horn just on the edge of stall (5 knots over stall airspeed). On landing, because the trim had to be so nose down for a "safe" takeoff, the perfect landing was very flat (3-point). And this was only if the last oscillation was nose down, then a touch of power to flare. Too much power and the nose would come up again and then try to slam back down. Too little power and we'd get a nose first arrival. I wonder if the trim required for a survivable aerotow would result in too much speed if not re-adjusted for landing (in most gliders). Although putting C.G. further aft reduces the need to retrim for landing, this creates more radical oscillations for landing, so it's a tough tradeoff/that might not be a good option... From the very enlightening posts of others, it seems the location of the tow hook and the angle of incidence of the wing vs. horiz. stab would be important factors. It also seems that winch is more forgiving (glider ends up at high altitude with surprised pilot) of no elevator than aerotow (where the glider just pulls the towplane tail up, and then the glider is off tow with a surprised pilot very close to the ground). Since the three assembled aircraft I've soloed have easily inspectable external elevator hookups, this is a bit academic, but I'd love to try dampening the oscillations with spoilers, and then try it using rudder only. Very interesting and perfectly suited to that calm winter air :-) |
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