Piper crop spraying type crash in Mexico.

[megan]

You Tube

[MechEngr]

That video is a bit off. The curve as weight decreases scales rather than shifts to the left by the square root of the ratio of the actual weight over the maximum weight. This is because the dynamic pressure, and therefore the resulting lift at a particular airspeed and AoA, varies as the square of the airspeed. Cut the weight in half and, for a given AoA, the plane will need 70.7% of the original speed (sqrt(1/2)) to develop matching lift.

Not sure about this case as I don't know how much water was on board, but if it was 1000# of water and max wgt of 2900#, then the factor for reaching stall AoA for a particular load factor will be scaled left by 0.8, so the maneuvering speed, by that calculation should be 80% of the fully loaded case.

I feel like I am missing why the maximum load factor doesn't go up as the aircraft is lighter. Sure, by 8 or 9 Gs the pilot is the limiting participant, but design for fatigue life results in higher attachment capacities. It also doesn't seem clear why where the payload is stored makes no difference to the maximum load factor. Putting that container on a wingtip would certainly change the characteristics in a way the simple calc fails to capture.

[IFMU]

Originally Posted by MechEngr

I feel like I am missing why the maximum load factor doesn't go up as the aircraft is lighter.

Pretty hard to calculate allowed G loading on the fly. Plus if the actual loads are lower from being under gross, that is adding margin to the life of the aircraft.

My aircraft is rated 4.4G at gross, and 6G at aerobatic gross. What if I'm 20 lbs under aerobatic gross? Can I pull 6.2G? What aircraft manufacturer wants to give a pilot that leeway?

[Pilot DAR]

I feel like I am missing why the maximum load factor doesn't go up as the aircraft is lighter.

Mathematically, it does. But, there will not be any approved data to support operations into that corner of the envelope. The limiting G factors are prescribed by the design standards and regulation, not convenience to the pilot for pushing it.

If a pilot chooses to pull really close to the G limit on a decades old airplane, I hope that they know its airworthiness intimately!

[Uplinker]

Out of interest, do small aircraft like this and others have C and D checks, as airliners do?

[EXDAC]

Originally Posted by Uplinker

Out of interest, do small aircraft like this and others have C and D checks, as airliners do?

No, they don't, at least not in USA. Typically, for non commercial use, an annual inspection is required. In commercial use a 100 hour inspection may be required if 100 hours reached before the next annual inspection is due.

Airworthiness Directives may impose addition inspection requirements.

[megan]

I feel like I am missing why the maximum load factor doesn't go up as the aircraft is lighter

Because such things as the battery container, engine mounts etc are designed to support the unchanging weight of the respective items to the certified "g" limit, going beyond the certified limit will over stress those respective mounts. Don't think there are many pilots who would appreciate their engine falling off..

[markkal]

Originally Posted by megan

Because such things as the battery container, engine mounts etc are designed to support the unchanging weight of the respective items to the certified "g" limit, going beyond the certified limit will over stress those respective mounts. Don't think there are many pilots who would appreciate their engine falling off..

The G'load neither up or down when the A/C is lighter or heavier, It's the stall speed that is affected. A heavier aircraft will stall at a higher velocity than a lighter one for the same amount of G's applied.

[ZeBedie]

Is there a CofG change when the hopper is dumped?

[IFMU]

Originally Posted by ZeBedie

Is there a CofG change when the hopper is dumped?

The hopper on a Pawnee is on the CG.