Is the MEI worth it?
11-06-2006, 07:24 AM
#21
Prime Minister/Moderator
Joined APC: Jan 2006
Position: Engines Turn Or People Swim
Posts: 39,224
Generally it is calculated/determined with the gear up, as this is less favorable froma stability point of view (typical twin). The gear being up is obviously a performance benefit, but Vmc is all about yaw stability. not performance.
11-06-2006, 12:41 PM
#22
On Reserve
Joined APC: Nov 2006
Posts: 15
Just a few comments
For a light twin engine a/c (under 6000 lbs with reciprocating engines)
The T in CASTBOW is Takeoff configuration
1. Flaps set to normal T/O position
2. Trim set for takeoff
3. Cowl flaps open
4. Gear up
For a/c over 6000 lbs Vmc must also be demonstrated in the landing configuration
1. Trimmed for approach with engines operating at Vref power that gives an approach gradient equal to steepest used in the landing distance demonstration FAR 23.75
2. Flaps in landing position
3. Landing gear extended
FAR 23.149
Also gear and its stabilizing effect does have some controversy about it and appears to be very airplane specific. In Australia they teach that gear has a negative effect on stability because once the plane is slipping through the air the gear (keels) will cause a greater yawing moment that the rudder must overcome.
Large gear doors forward of CG (nose gear) would exacerbate this negative quality. While gear doors aft of CG would help stabilize the a/c.
The less mentioned item about gear and its ability to stabilize the a/c is that it slightly lowers CG which will have a positive stabilizing effect.
For a light twin engine a/c (under 6000 lbs with reciprocating engines)
The T in CASTBOW is Takeoff configuration
1. Flaps set to normal T/O position
2. Trim set for takeoff
3. Cowl flaps open
4. Gear up
For a/c over 6000 lbs Vmc must also be demonstrated in the landing configuration
1. Trimmed for approach with engines operating at Vref power that gives an approach gradient equal to steepest used in the landing distance demonstration FAR 23.75
2. Flaps in landing position
3. Landing gear extended
FAR 23.149
Also gear and its stabilizing effect does have some controversy about it and appears to be very airplane specific. In Australia they teach that gear has a negative effect on stability because once the plane is slipping through the air the gear (keels) will cause a greater yawing moment that the rudder must overcome.
Large gear doors forward of CG (nose gear) would exacerbate this negative quality. While gear doors aft of CG would help stabilize the a/c.
The less mentioned item about gear and its ability to stabilize the a/c is that it slightly lowers CG which will have a positive stabilizing effect.
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