Ask d10 about flying helicopters and win $$$

[d10]

I have a check ride on Monday. I should be studying for it, but I'd rather play poker. So ask me anything you want to know about flying helicopters. Mechanical functions, aerodynamics, IFR/VFR flight, FAA regulations, whatever. I can probably answer anything Black Hawk specific, I may or may not be able to answer questions about the other US Army helicopters, and I probably can't tell you anything about civilian model helicopters, unless it's a general question.

If you ask me something that I need to look up and I get asked the same question on my check ride, or if you ask anything that I feel in any way allows me to realize an actual benefit on my check ride, I'll transfer you $25 via whatever method you want. I'll make the final determination on what qualifies, and it will be an entirely subjective decision, so you'll just have to trust that I value my integrity more than $25.

[TTChamp]

What actions do you take for an electrical system failure?

[d10]

[ QUOTE ]
What actions do you take for an electrical system failure?

[/ QUOTE ]

This depends on a lot of stuff. Helicopters will either be designed so that the important stuff (engines, flight controls, various instruments) function just fine without electrical power, or the more complicated helicopters will have so many redundant electrical systems that a complete failure is incredibly unlikely.

A Black Hawk has an alternator on each engine to power engine specific electronics. If they fail, you will need to manually control the affected engine. Not a big deal.

There are 2 AC generators which feed into 2 DC converters to provide AC and DC power for normal operation of everything else. All the other electronics are run off of various busses that can be powered by either generator or by battery power. The busses allow the less important components to be shut down as necessary, and the more important components to receive power from numerous sources. If I lost 1 generator, I would try to get it back online, if that doesn't work, just shut it off and everything will run fine on the other generator. If both generators fail, again try to get them back online, if that fails I can start up the APU (auxiliary power unit, a smaller engine not connected to the rotor system used for the sole purpose of electrical/hydraulic/pneumatic power) and use the generator off of that. In any case, the helicopter is still fairly safe to fly, but if I wasn't on a really important mission or something, I would turn back home.

[econophile]

how heavy of a load can a blackhawk safely lift?

[Reef]

explain torque's effects on the helicopter fuselage in general, in tip-jet helicopters, and in single main rotor helicopters.

explain means for torque compensation in single main rotor helicopters.

Fill in the blank:

During hovering flight, the single rotor helicopter has a tendency to drift laterally to the right due to the lateral thrust being supplied by the tail rotor. The pilot may prevent right lateral drift of the helicopter by _____________________________

[d10]

[ QUOTE ]
explain torque's effects on the helicopter fuselage in general, in tip-jet helicopters, and in single main rotor helicopters.

explain means for torque compensation in single main rotor helicopters.

[/ QUOTE ]

It's just a simple case of Newton's 3rd law, action/reaction. Pushing torque out to the main rotor will cause a torque effect on the fuselage in the opposite direction. Tip-jet helicopters get around this by powering the rotor from the rotor tips themselves, so there is no need for a tail rotor. There will be some amount of friction between the rotor and the fuselage, so the fuselage will have a tendency to rotate in the same direction as the rotor. I don't know much about tip-jets, but I imagine they suck at hovering. With enough airspeed they can probably do fine with a rudder.

In a single rotor helicopter, a tail rotor is used to provide thrust to counteract the torque of the main rotor. The tail rotor is linked mechanically to the main rotor so that they rotate at proportional speeds. Some method of changing the pitch angle of the tail rotor blades will be in place to change the amount of thrust the tail rotor puts out to maintain directional control under different loads, and to allow the pilot to turn the helicopter at a hover or low speeds. Some kind of vertical fin is also common near the tail rotor for stability at higher speeds, so as you increase airspeed, there is less requirement for tail rotor thrust, which allows more engine power to be used for the main rotor.

[ QUOTE ]
Fill in the blank:

During hovering flight, the single rotor helicopter has a tendency to drift laterally to the right due to the lateral thrust being supplied by the tail rotor. The pilot may prevent right lateral drift of the helicopter by _____________________________

[/ QUOTE ]

left cyclic. Some helicopters will have a left tilt built into the transmission, or have the controls rigged so that a centered cyclic will actually cause a slight left tilt in the rotor disc. Beyond that, some helicopters will use electronic actuators to compensate for this effect as necessary. But the only action the pilot can take is left cyclic.

[d10]

[ QUOTE ]
how heavy of a load can a blackhawk safely lift?

[/ QUOTE ]

The cargo hook for a UH-60A is rated at 8,000lbs. For a UH-60L it's rated at 9,000lbs. Either way, you'll never be able to lift that much. Basic weight is typically around 13,000lbs, add 2400 for full fuel, 1000 for 4 crewmembers and their gear, you're at 16,000 something operating weight. Max gross weight is 22,000 lbs, so you're looking at about 6,000lbs to spare on a good day.

One time I was working a standby mission during a brigade sized air assault and a Chinook had to go down for maintenance. They asked my crew if we could lift their load, since it was "only" 6,500lbs. We checked our numbers and it looked close, so we gave it a try. We came up to a hover showing 135% torque. Allowable range is up to 120% for continuous operation at less than 80 knots, and up to 144% for 12 seconds max. We figured once we got through ETL it would drop to under 120, and it did, so we flew it out of there. It was so heavy that just the slight rocking back and forth under us would pull our airspeed down, then back up, back and forth the whole way there. I got a little bit sick, but it was a short trip so it was all good. I'd say that's about as much as a Black Hawk can safely lift. Maybe a little more than safe, I wasn't the PC on that flight.

[Reef]

Fill in the blanks and explain each one

[d10]

[ QUOTE ]
Fill in the blanks and explain each one



[/ QUOTE ]

From left to right:
Rotational relative wind: The direction of airflow relative to the wing
Angle of attack/incidence: Angle between the chord line of the wing and resulatant/rotational relative wind (respectively)
Lift: Aerodynamic force opposing gravity
total aerodynamic force: lift+drag
Drag: Aerodynamic force produced by wind resistance
chord line: imaginary line between leading and trailing edge, lots of aerodynamic stuff goes on along this line

2nd picture points to a lot of the stuff in the first, with the addition of the leading edge and trailing edge, which is self explanatory.

[Reef]

What is pressure altitude?

What is density altitude?

What do you need to find density altitude?