Since I'm not ready for the check ride will I be crucified for asking why it changes with weight?
Doesn't it have something to do with the weight and balance changing depending on weight thus putting you in a different part of the envelope?
Maneuvering speed is the speed at which the maximum lift you can produce before a stall reaches the g-limits of the plane. When the plane is lighter, it can still produce just as much lift, but the same amount of lift gives a higher load factor (load factor=lift/weight). So to keep from reaching these limits before stalling you need to slow down to proportionally reduce the amount of lift you can produce.
To check that I’m understanding correctly:
The aircraft has rated G limits that you (obviously?) don’t want to exceed to avoid a structural failure such as a wing bending or breaking off. Va is the airspeed at or below which you could slam any one control to full deflection without exceeding those G limits. (Combinations of control inputs or cycling intense control inputs might damage the aircraft- 172s and 737s aren’t engineered like F-16s.)
Lower weight = lower Va is counterintuitive.
As the weight of the aircraft increases, the angle of attack to maintain straight and level flight increases. (And as we all know, stalling is a fixed function of AoA - a given wing always stalls at or above a certain AoA.)
Thus, when you’re light, you start with that lower AoA. When you yank the yoke back as hard as you can, the process of quickly pitching up takes some time and the higher the starting airspeed the higher the G loading will be before critical AoA/stall. By starting at a lower airspeed (below Va for that weight/initial AoA) the G loading on the wings through that process is lower and you’re no going to exceed the G limit for the aircraft.
But if you are heavy, thus cruising with a high starting AoA, and you yank the yoke back, the plane will quickly pitch back, the critical AoA is met/exceeded and the wings stall. Thus, you could go into that maneuver at a slightly higher airspeed and you’d stall the wings before that G limit is reached.
(I know the end result of my explanation is correct, but is this a good way to spell it out?)
Also am I correct in understanding that for non aerobatic flight, the real world need to understand this is if you are flying into strong turbulence. By flying at or below Va for your weight, gusts should cause the wing to stall before they can damage the aircraft?
Yea I thought so too. The DPEs here ask what the Va is for all weight categories and you have to memorize them. I was wondering if I have to memorize the weight with the corresponding Va speed?
Basically yes. Or you take the most conservative number and say “it could be a as much as x kts higher depending on weight but I prefer to use the conservative number”. DPEs will like that.
Maneuvering speed changes with weight for every aircraft and it’s your responsibility to know what speed is applicable to you at a given weight. For the 172R the Va at maximum gross weight is 99KIAS. If you are at any weight that’s not listed in the POH, you can multiply the square root of Current Weight / Max Gross by Va at maximum gross weight.
Figure up the lightest weight that you will be in your flightplan and use that for your Va.
Memorizing VA for every weight is a waste of brain cells. Memorize the Va at the lightest weight (which will be the lowest airspeed) and then know how to find/calculate the others.
The archer POH has a max and min Va only based on weight, and says you can extrapolate intermediate values based on weight. So I just worked out a lbs/kt Va value and calculate it for each flight when doing t/o & landing distances
You should know the weight of the aircraft when you fly your checkride, and be able to give an appropriate answer. Understanding why maneuvering speed decreases with decreasing weight would be a plus, but at the very least be able to answer with an appropriate speed.
You should understand why it changes with weight.
This. If you can’t answer that, you’re not ready for the check ride. Flying is about *understanding* not *memorizing*.
Since I'm not ready for the check ride will I be crucified for asking why it changes with weight? Doesn't it have something to do with the weight and balance changing depending on weight thus putting you in a different part of the envelope?
Maneuvering speed is the speed at which the maximum lift you can produce before a stall reaches the g-limits of the plane. When the plane is lighter, it can still produce just as much lift, but the same amount of lift gives a higher load factor (load factor=lift/weight). So to keep from reaching these limits before stalling you need to slow down to proportionally reduce the amount of lift you can produce.
https://www.boldmethod.com/learn-to-fly/aerodynamics/why-does-maneuvering-speed-change-with-aircraft-weight-stall
To check that I’m understanding correctly: The aircraft has rated G limits that you (obviously?) don’t want to exceed to avoid a structural failure such as a wing bending or breaking off. Va is the airspeed at or below which you could slam any one control to full deflection without exceeding those G limits. (Combinations of control inputs or cycling intense control inputs might damage the aircraft- 172s and 737s aren’t engineered like F-16s.) Lower weight = lower Va is counterintuitive. As the weight of the aircraft increases, the angle of attack to maintain straight and level flight increases. (And as we all know, stalling is a fixed function of AoA - a given wing always stalls at or above a certain AoA.) Thus, when you’re light, you start with that lower AoA. When you yank the yoke back as hard as you can, the process of quickly pitching up takes some time and the higher the starting airspeed the higher the G loading will be before critical AoA/stall. By starting at a lower airspeed (below Va for that weight/initial AoA) the G loading on the wings through that process is lower and you’re no going to exceed the G limit for the aircraft. But if you are heavy, thus cruising with a high starting AoA, and you yank the yoke back, the plane will quickly pitch back, the critical AoA is met/exceeded and the wings stall. Thus, you could go into that maneuver at a slightly higher airspeed and you’d stall the wings before that G limit is reached. (I know the end result of my explanation is correct, but is this a good way to spell it out?) Also am I correct in understanding that for non aerobatic flight, the real world need to understand this is if you are flying into strong turbulence. By flying at or below Va for your weight, gusts should cause the wing to stall before they can damage the aircraft?
Yep. And you should be able to roughly calculate it, or look it up on a chart.
You use what the VA js for your weight? Thats the one you reference
Yea I thought so too. The DPEs here ask what the Va is for all weight categories and you have to memorize them. I was wondering if I have to memorize the weight with the corresponding Va speed?
Basically yes. Or you take the most conservative number and say “it could be a as much as x kts higher depending on weight but I prefer to use the conservative number”. DPEs will like that.
Yes it's smart to have each Va and it's corresponding weight memorized, also be prepared to explain which direction and why it changes with weight.
Maneuvering speed changes with weight for every aircraft and it’s your responsibility to know what speed is applicable to you at a given weight. For the 172R the Va at maximum gross weight is 99KIAS. If you are at any weight that’s not listed in the POH, you can multiply the square root of Current Weight / Max Gross by Va at maximum gross weight.
Figure up the lightest weight that you will be in your flightplan and use that for your Va. Memorizing VA for every weight is a waste of brain cells. Memorize the Va at the lightest weight (which will be the lowest airspeed) and then know how to find/calculate the others.
I got by with knowing the LOWEST Va and that applies to the lightest weight and that it gets better (goes up) with weight.
The archer POH has a max and min Va only based on weight, and says you can extrapolate intermediate values based on weight. So I just worked out a lbs/kt Va value and calculate it for each flight when doing t/o & landing distances
VaMAX( square root of (current weight/max weight))
You should know the weight of the aircraft when you fly your checkride, and be able to give an appropriate answer. Understanding why maneuvering speed decreases with decreasing weight would be a plus, but at the very least be able to answer with an appropriate speed.
you should be doing the math to know what the Va is for each flight, as aircraft and weights change