Fly2HMO
Posts: 7207
Joined: Sat Jan 24, 2004 12:14 pm

? On Pusher Twin Props And Vmc Speeds

Sat May 26, 2007 9:43 am

I was wondering if pusher props, such as the Beech starship or the Piaggio Avanti are susceptible to Vmc rolls, or if they even have a Vmc speed. My guess is that they do, but its probably not as bad as a normal twin airplane (say a PA-44) because there is no accelerated slipstream over the wing.

Feel free to add-to, modify, or butcher my hypothesis. Big grin
 
2H4
Posts: 7960
Joined: Tue Oct 19, 2004 11:11 pm

RE:? On Pusher Twin Props And Vmc Speeds

Sat May 26, 2007 10:16 am




Quoting FLY2HMO (Thread starter):
or if they even have a Vmc speed.

I have a Business & Commercial Aviation pilot report on the P-180. Here's an interesting excerpt:

Quoting BCA Pilot Report:
At FL 350 we excited the Dutch roll for another look at the Avanti’s lateral/ directional characteristics, and without any stability augmentation devices the aircraft exhibited good damping, returning to steady flight in six cycles.

Spiral stability was also very good, with almost no tendency for the Avanti to continue into a spiral when the controls were freed after the aircraft was placed in a 10-degree bank. Adverse yaw is minimal, thereby negating the need for any unusual compensation with rudder coordination.

Also, the aircraft’s ailerons have a comfortably light feel, and roll rate is well over 30 degrees per second, which Piaggio engineers feel might be a little too spritely for a typical corporate aircraft. I thought the Avanti behaved nicely in all aspects of its lateral/directional handling, however.

The aircraft also performed equally well in pitch; all modes of stability were well damped, and control was authoritative. The Avanti felt very much at home at FL350, responding smartly to my control inputs and not balking at large changes in attitude as we attempted steep turns and roll-rate checks.

After the look at high speed handling, we descended to FL 200 for a brief feel of one-engine-inoperative flight. While Piaggio engineers have yet to determine VMC in flight, which they estimate will be about 100 knots, we shut down one PT6 and experienced no unusual characteristics at cruise airspeed.

2H4


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Fly2HMO
Posts: 7207
Joined: Sat Jan 24, 2004 12:14 pm

RE:? On Pusher Twin Props And Vmc Speeds

Sat May 26, 2007 1:24 pm

Quoting 2H4 (Reply 1):
While Piaggio engineers have yet to determine VMC in flight, which they estimate will be about 100 knots

Hmm. Interesting indeed. You'd figure they'd know that by now...
 
MD-90
Posts: 7835
Joined: Mon Jan 17, 2000 12:45 pm

RE:? On Pusher Twin Props And Vmc Speeds

Sat May 26, 2007 2:27 pm

Quoting FLY2HMO (Reply 2):
Hmm. Interesting indeed. You'd figure they'd know that by now...

Must've been an early report, as I believe they'd need to know that for certification. Big grin

I wonder what the stall speed is?
 
2H4
Posts: 7960
Joined: Tue Oct 19, 2004 11:11 pm

RE:? On Pusher Twin Props And Vmc Speeds

Sat May 26, 2007 10:20 pm




Quoting MD-90 (Reply 3):
Must've been an early report

Yep, sure enough. Looks like September 1987.

Found some more info. From Airportjournals.com

Operating speeds on the Avanti are stall speed in the landing configuration, 93 KIAS; maximum operating speed, 260 KIAS or 0.7 Mach; maximum flap operating speed for MID position, 170 KIAS, and DN position, 150 KIAS; and maximum flap extended speeds, 180 KIAS for flaps MID and 175 KIAS for flaps DN.

Maximum landing gear operating speed is 180 KIAS, and the maximum landing gear extended speed is 185 KIAS. Minimum control airspeed is 100 KIAS, with rotation speed, at 11,550 lbs, 106 KIAS. Best rate of climb speed is 160 KIAS; best angle of climb speed, 140 KIAS; and maneuvering speed, 199 KIAS.



2H4


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