Maneuvering Speed

[Mjg2011]

Since the lift equation is L=CL 1/2 p v^2 A and maneuvering speed depends solely on lift produced (given that weight is constant) (load factor = lift/weight), does maneuvering speed also change with air density because density affects lift produced?

If the air is more dense, you will be at a lower angle of attack for a given airspeed to maintain level flight, so after pulling on the stick, your load factor will be more by the time you reach your critical angle of attack than it would at a warmer temperature or lower pressure.


I am also wondering this for stall speed but am not as concerned because an aircraft can stall at any speed and attitude anyway.

 

[midwestpa24]

Think about this...is maneuvering speed and stall speed IAS or TAS?

 

[luvflyin]

Since the lift equation is L=CL 1/2 p v^2 A and maneuvering speed depends solely on lift produced (given that weight is constant) (load factor = lift/weight), does maneuvering speed also change with air density because density affects lift produced?

If the air is more dense, you will be at a lower angle of attack for a given airspeed to maintain level flight, so after pulling on the stick, your load factor will be more by the time you reach your critical angle of attack than it would at a warmer temperature or lower pressure.


I am also wondering this for stall speed but am not as concerned because an aircraft can stall at any speed and attitude anyway.

The ‘density’ that acts on the plane is the same density that acts on the pitot tube that gives you airspeed. So Va doesn’t change. Same thing with stall speeds. You’ll be moving faster over the ground with less density, but the plane don’t care about that.

EDIT: like the True Airspeed comparison above.

 

[Clip4]

Since the lift equation is L=CL 1/2 p v^2 A and maneuvering speed depends solely on lift produced (given that weight is constant) (load factor = lift/weight), does maneuvering speed also change with air density because density affects lift produced?

If the air is more dense, you will be at a lower angle of attack for a given airspeed to maintain level flight, so after pulling on the stick, your load factor will be more by the time you reach your critical angle of attack than it would at a warmer temperature or lower pressure.


I am also wondering this for stall speed but am not as concerned because an aircraft can stall at any speed and attitude anyway.

Va would change slightly for CG. Keep in mind there is a safety margin involved with many aircraft limitations.

 

[dtuuri]

If the air is more dense, you will be at a lower angle of attack for a given airspeed to maintain level flight...

Says who? If the air is more dense, the angle of attack will be the same for a given indicated airspeed. That's the great thing about airspeed indicators—they're pseudo angle of attack indicators no matter what your density altitude is.

 

[William Pete Hodges]

The V speeds are indicated air speeds because IAS is derived from the dynamic pressure of the relative wind. The airspeed indicator is a simple differential pressure gauge calibrated to read airspeed at seal level on a standard day. Since it reads dynamic pressure instead of true airspeed, V speeds as IAS do not change, but actual airspeed at the same indicated speed changes with air density, From this perspective AOA vs IAS does not change with air density as the dynamic pressure is the same.

For an aircraft in stable steady flight, the indicated airspeed will correspond closely to the AOA at designed gross weight. So for gross weight, V-a will occur at the same IAS, and at the same AOA as long as the maneuver has time to stabilize. At less than gross weight less lift force required to hold the airplane up, so at the same AOA less dynamic pressure is necessary and IAS is lower.

During transitions from one stable condition to the next, the AOA (and wing load) changes almost immediately with control input by the pilot. However the inertia of the airplane delays a change of actual airspeed until the flight path and airspeed has time to catch up and stabilize. This can take several seconds to occur. AOA and Lift Reserve indicators show this to the pilot immediately as it is happening without the delay.

I got a litte long but I hope it helps.

 

[AlphaPilotFlyer]

If I may add something.....in test pilot class we were always told to keep is simple.

the airplane wing doesn’t care or know anything about TAS, air temperature, altitude humidity, etc... it only knows and cares about the resultant density and speed of airflow..... the airspeed indicator the same. Pilots really only need to know Va is based on stall speed (reaching critical AoA).... so it’s an IAS value, and Va increases with weight. If you really need to know more consider the following:

Va is simply a speed to help prevent us pilots from over stressing the structure by slowing us down enough so we will stall the wing (unloading the stress on airframe) before reaching design limits. The faster you fly, or lighter the GW, the lower your AoA, so the further you are from critical AoA and stalling....thus, the wing has plenty of lift left allowing you to exceed structural limits well before stalling. Stall speed is a function of weight (whether actual GW or from increased load factor...such as climbing or turning

the lighter you are, the lower your AoA, so potential lift can be more than the airframe can take from control inputs or turbulence (think of an abrupt updraft that changes relative wind....the further the wing is from crit AoA, the more lift left and potentially more stress produced before reaching critical AoA and stall). The heavier you are, you are already closer to critical AoA and a stall so you can fly faster as any further meaningful increase in loading will quickly stall the wing.

small aircraft publish Va at Max weight as the envelope between EOW and MGW is small. However, larger aircraft Va range is substantial. In fact, larger transport category aircraft have both a Va and Vb (turbulence penetration speed) which is essentially the same protection but specific to turbulence dynamics. Another similar speed, max cornering speed, is also based on similar requirements.

but again, more than most pilots need to really know......