Maneuvering Speed Explanation

aggiepilot87

Well-known member
Joined
Nov 26, 2001
Posts
120
Total Time
-
Anyone know where I can find a quantitative explanation of maneuvering speed? I mean one like a mathematical explanation. Conceptually, I understand, and can explain it in the general terms of limiting load factor and stall speeds varying with loading, but I need something more detailed. I have a phd astronomer as a student and she just keeps asking questions!!!

How about Aerodynamics for Naval Aviators? Does it have any quantitative explainations like this?

Thanks.
 

Rvrrat

Well-known member
Joined
Feb 5, 2002
Posts
139
Total Time
401
Perhaps draw a VG diagram on an infamous whiteboard and lable the areas "within design stress tolerances", "bend" & "break". Then use L=Cl x 1/2 x p x Vsquared x S
where L=lift Cl= coefficient of lift p=airdensity V=velocity S=wing area
to demonstrated the "squared" relationship between speed & lift; ie: trebling the speed begets nine times the lift.

Since stall speeds in the POH are generally given for max weight conditions; if we're flying at weights less than gross, the stall speed & maneuvering speed will be less.
For an example lets use a PA28R-200
Max gross weight of 2650 lbs. Va=114 kts
For this example use the following loading.
BEW=1613, Pilot=170, pax=160, bags=20, fuel=204 for a total of 2167 lbs.

2167/2650=.817 or, 81.7% of max gross

to get .817 times as much lift, find the square root of .817 which is .904 or 90.4% rounded to 90%; meaning we only need 90% of the airspeed required at max gross.

Ergo, Va at 2167 lbs = .90 x 114 kts = 102.6 kts or 103 kts.
 

GeorgeTG

Well-known member
Joined
Nov 25, 2001
Posts
52
Total Time
4500
I completely agree with the previous poster.

That’s a good way of calculating lower maneuvering speeds for weights below max gross weight.

If all you’re after is to calculate Va (maneuvering speed) this might help:

The key to being safe when it comes to maneuvering speed, is to limit the aircraft's ability to generate lift.

The easiest way to limit lift is by controlling speed (reference lift equasion in previous post)

The objective of maneuvering speed is to have the aircraft stall prior to reaching limit load.

1.) Lift increases at the square of speed
(twice the speed, four times the lift)

2.) Stall speed is the speed at which Lift = Weight
(ok, so actually lift is a smidgen below weight)

3.) The square root of the limit load;
times the stall speed = Maneuvering speed

Example:

Let’s say Vs = 50Kts

Lift = Weight ... lets call that 1g

Let’s say we have an airplane with a positive limit load of 4g

We want to find the speed were we can generate 4 times the lift.
This will be our Maneuvering Speed.

If we DOUBLE our speed to 100Kts, we’ll have FOUR times the lift.
Let’s call that 4g

100Kts is our maneuvering speed.

Use the square root of the limit load for your aircraft 3.8, 4.4 whatever
Multiply that by your stall speed at your weight.
That’s your maneuvering speed.

Cheers
George
 
Top