# Tag Info

53

No, the helicopters are standard production versions. The Eurocopter AS350 is a common model used for these operations. In 2005, Didier Delsalle landed a Eurocopter AS350 B3 on the summit of Mt. Everest at 29,029 feet (8848m) (twice). The only changes he made to the standard version were removing a few things like extra seats to reduce the weight, and of ...

27

Well, that’s complex. Where should I begin? The main job of the tail rotor is to use its long lever arm and directed force/thrust (horizontal lift) to counteract the torque of the spinning main rotor. The exhaust gas of a Turboshaft engine does not produce a large amount of thrust for the very large amount of torque the rotor-powertrain combination produces....

25

Discounting the V-22 Osprey and the other tiltrotors, the drawbacks are: Wasted cabin space L-duct inlet(s) needed to guide the air in With that potential problems with getting the air in as the air prefers fewer turns A reduction gearbox is still needed Gearbox still needed for the tail rotor Harder maintenance access as it will be buried into the fuselage ...

15

No a turboshaft cannot directly drive the rotor without a reduction gear, the rotor torque is too high for the ungeared turbine torque. The rotor blades are much longer than those of a prop or fan (relatively) and the rotor turns slower, a definite case for torque gearing. Mounting the engine vertically saves a 90 deg gearing assembly, but places the engine ...

9

The first figure, 1 litre per mile, is very wrong. The second, 39 to start, is most probably the fuel required for a warm up from a cold start. The Abrams tank weighs 62 tonnes, so you won't get 1 mile on a litre. Its fuel consumption is quoted as 0.6 mpg, or 1.66 gallons per mile, which is 6.3 litres per mile. Quite a difference. The engine is the ...

9

Yes, the exhaust of any engine does provide some thrust (very little for piston engines). The amount of jet thrust for turboprops is in the range of 4%-15% of propeller-produced thrust. For a helicopter, it's only 2%-4% of rotor lift, but it's directed backwards. The helicopter in your picture would get 100-150 lbf of thrust from the engine exhaust, ...

8

The turbine output is very hot and therefore needs to be shielded in some way if it is to be routed through any part of the helicopter. This shielding adds cost and weight, so it's generally avoided. The turbine itself is situated very near the center of gravity of the helicopter, so the turbine output has very little leverage on the helicopter's rotation ...

6

The turbine engine of a helicopter has very little exhaust thrust. They are turboshafts, designed to extract every bit of useful energy for driving the main rotor shaft. From Wikipedia: A turboshaft engine is a form of gas turbine that is optimized to produce shaftpower rather than jet thrust. In concept, turboshaft engines are very similar to turbojets, ...

5

The main way to convert a gas turbine to provide thrust rather than shaft horsepower is to attach a large fan or propeller in place of the previous load. For example, the GE CF6, which powers aircraft such as the 747, 767, and A330, has a gas turbine variant called the LM6000 that provides around 50 MW of power. If you want to provide thrust from the ...

3

The reason a Diesel engine has a torque figure and a horsepower power figure is because max torque and max horsepower occur at different engine RPMs. Have a look at any performance curves of a piston engine and this will be evident. Hence, to define in a few numbers the maximum performance of the engine, you need to give both figures. However, turboprop ...

3

This is a very good question. However, there is a slight error in your question, which is causing the confusion. Turbine power, is determined by the ratio of total pressure across the turbine (and other factors). See the formula here on NASA’s website. $$W_{Turbine} = \eta \cdot c_p \cdot T_{t_4} \cdot \left( 1-TPR^{\frac{\gamma-1}{\gamma}} \right)$$ ...

3

I think your friend is playing a joke on you. I have worked with helicopters since the late 1970's and there is no way to distinguish military from civilian simply by engine noise. You may be able to distinguish between models of helicopters, and in so doing identify a model used by the military versus a civilian one, but that's about it.

3

Stan Hiller's earliest helo designs were coaxial and used relatively small 4-cylinder aircraft engines to drive the coax transmission, so it is indeed possible to power a small coaxial helicopter with a relatively small piston engine. Hiller also found that autorotating a coax main rotor blade setup was difficult and so his later designs used a more ...

3

Your question: Here is a section view of a sample and I indicated the connection area. What type of connection elements are used there? Anything related will be helpful. From the title of your question I guess you assume the bolted element is a HPC rotor, and you might be wondering why a rotor would be bolted to a stationary element, the fan frame. Indeed ...

2

In effect, this question is related to In a turbofan what holds the spinning axis?. This question has an excellent answer that closely relates to this question (but isn't a duplicate). The following figure is re-posted for a relevant answer. Credits go to user mins. HP rotors of CFM56-7B. Adapted from CFM56-7B Familiarization Manual This answer hints to ...

2

You can only use for shaft horse power what is available after the energy to drive the compressor is subtracted. This subtraction is done by the high pressure turbine. Any energy left in the exit flow after that can be extracted to drive a propeller, a fan or a generator. What happens in your arrangement if the power turbine extracts too much energy to keep ...

2

I suppose the F135-PW-400 powerplant on the F-35B does just that. A turbine engine is used to create high enthalpy gas which can either pass through a turbine to produce mechanical work or pass through a diffuser to accelerate it and create a reaction impulse. General Electric has designed power generation gas turbines which use the gas core from the GE ...

2

Most turbine engines designed to drive some sort of mechanical system such as a hydraulic pump and electrical generators are not designed to provide thrust because their fuel controller can only run it at one speed. In other words, there is no throttle. Also, the internal components may not be designed for that type of application. So while it is in theory ...

1

Because it's less useful for aviation application. For diesel and electric, or ground vehicle and industrial motors in general, lack of peak torque is a problem (engine/motor stall), but for aviation, there's never a condition that you can stall a turbine. Usually you stall the propeller way before you stall a turbine. Or, put it another way, an aviation ...

1

Thanks for the discussion - Penguin. However, for reasons below, I am not convinced of your explanation. The formula for turbine power you quote is for a turbofan engine. For a turboshaft engine, where the exit kinetic energy is wasted, the pressure ratio and the efficiency used is inlet total to exit static. In addition, in your thrust equation above, you ...

1