I'm studip

[AVI8V1]

I have a question: Do Vy and Vx change with weight? I know Va does. Do they change with altitude? I know Vs doesn't.

 

[banned username 2]

I'm studip

You're also Dyslexic, "Stupid" is spelled with the P before the D...

Sorry, I couldn't resist...

 

[AVI8V1]

yeallr? I tidn'd eealizr ThaT.

 

[bobbysamd]

Vy and Vx

It depends on the airplane. Vx and Vy stays the same for most light airplanes. Take a look at your POH; it might quote Vx and Vy at max gross and say the speeds can be used at lower weights.

 

[AVI8V1]

What about something the size of a seneca? I do not think they change but I've heard different thoughts, not sure of the sources. Could just be their own misconceptions.

 

[bobbysamd]

Seneca Vy/Vx

What about something the size of a seneca? I do not think they change but I've heard different thoughts, not sure of the sources. Could just be their own misconceptions.

I don't know. For what it's worth, Seminoles, which are smaller, kept the same V speeds.

It is primarily a function of weight. V speeds for "large" aircraft, i.e. those >12,500 lbs., will be different as loading changes. But for smaller spam cans, V speeds don't change that much at all.

Hope that helps some more. As always, the approved POH is your final source on operating your airplane.

 

[acabello]

In the cessna 172 Vy and Vx change with altitude but you should look in you poh or pim to get the facts for your airplane. Look and see what configuration the plane is in when they get those speeds I beleive it is usually always clean but I could be wrong, for instance if Vy is 78 in clean configuration but you have gear down then it may be something like 75. Also remember that these speeds are pitch attitudes which explains my previous statement, if Vx is 64 at 10deg. pitch up and you put the gear down and hold the same pitch attitude you will slow down.I could go on and on about the factors that come into play with this but I have had to read it all in books so you should to.

 

[Singlecoil]

I have a question: Do Vy and Vx change with weight? I know Va does. Do they change with altitude? I know Vs doesn't.

They change with weight and altitude. The numbers in your POH are for gross weight at sea level on a standard day.

The formula for speeds at other weights (if memory serves) is:

The square root of current weight divided by gross weight. Take that number and multiply it by any V speed and that is the correct V speed for your current weight.

Ex. 4000 pound gross weight, Vy is 75 knots. Current weight is 3500 pounds. 3500 divided by 4000 is .875. Take the square root of that and you get .935. Multiply that by 75 and you get 70 knots. That works for stall speeds, approach speeds, climb speeds etc. Very helpful for short field landings at light weights.

Vx and Vy change with altitude as well. Vx gets higher with altitude, Vy gets lower. They converge at the absolute ceiling of the airplane (zero rate of climb).

 

[bobbysamd]

Vx and Vy converging

I agree with the above. I remember the graph now.

 

[AVI8V1]

That's it! Thank you all so much. I feel much less more studip now.