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maneuvering speed?

C

cjohngraham

Member
How does one determine maneuvering speed for an aerobatic category aircraft? I've read that Va is usually 1.4xVs, but if maneuvering speed is the speed at which you will stall before bending the airplane, seems it must be higher. For a -7A, I've seen 122 kias in one owner's POH. Is that reasonable?
 
Varies with aircraft weight

Assuming an aerobatic weight for an RV-7(A) of 1650 pounds, you need to determine your 1G stall speed (clean). Multiply that times the square root of the aerobatic load factor of 6 positive G's (2.45) will give you the maneuvering speed at that weight. Keep in mind the maneuvering speed decreases with decreasing weight. Seems counter-intuitive but as the weight decreases so does the 1G stall speed.
 
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Academic Question:

assuming you have a G meter, couldn't you load the airplane to the acro weight and pull 6 Gs in a level turn and see if it will stall?
 
Thanks much, that's what I was looking for. Based on my Phase 1 results, that's a Va of 132 kias. At the high DAs in New Mexico, about the only time I see that speed is in a dive to get speed for an acro maneuver, so good to know.
 
cjohngraham said:
Thanks much, that's what I was looking for. Based on my Phase 1 results, that's a Va of 132 kias. At the high DAs in New Mexico, about the only time I see that speed is in a dive to get speed for an acro maneuver, so good to know.
Click to expand...

Just make sure that stall speed was determined at 1650 pounds. If you did the stall tests at 1800 pounds, your stall speed at 1650 would be about 4% less (square root of 1650/1800 times stall speed at 1800 pounds).

Double check my calculations, the aero engineering stuff is pretty atrophied. Hopefully Steve Smith or another more current aero type will chime in if I've led you astray.
 
flyinhood said:
Academic Question:

assuming you have a G meter, couldn't you load the airplane to the acro weight and pull 6 Gs in a level turn and see if it will stall?
Click to expand...

Good thought, but at age 70, I'm not inclined to go to 6Gs, and if the plane did something funny after such a stall, it could be an oily mess, since zero/negative Gs blow oil out the breather. That happened in a hammerhead stall in Phase 1, and oil still seeps from seams in the skin 2 years later.
 
KatanaPilot said:
Just make sure that stall speed was determined at 1650 pounds. If you did the stall tests at 1800 pounds, your stall speed at 1650 would be about 4% less (square root of 1650/1800 times stall speed at 1800 pounds).

Double check my calculations, the aero engineering stuff is pretty atrophied. Hopefully Steve Smith or another more current aero type will chime in if I've led you astray.
Click to expand...

Yes, thanks, I'm aware of the Va variance with weight, and at some point will go back and recheck stall speeds at various weights. The plane isn't yet painted and I'm going to put on a heavier crush plate to move CG forward, so will do that once we're at something like a "final" configuration.
 
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