37

Let's see how many things we can find wrong. There's a bang, smoke starts coming from the exhaust. Master caution comes on and his first response is to tap and check the 115v AC gauge! The pilot takes his hand off the collective! You hear the engine wind down and the rotor RPM drop. He announces a gearbox failure. So why did the engine wind down? His ...


37

Helicopters are able to do something called autorotation if all thrust is lost. In a helicopter, an autorotative descent is a power-off maneuver in which the engine is disengaged from the main rotor system and the rotor blades are driven solely by the upward flow of air through the rotor. In other words, the engine is no longer supplying ...


34

When the engine fails in a single engine helicopter it can autorotate back to earth: it gives up potential energy from reducing height to keep the rotor turning, which then continues to provide lift. Autorotation can take place straight downwards in vertical flight, but the general recommendation is to maintain forward speed, like a fixed wing gliding: the ...


30

I am going to assume that by "critical", you mean survivable. I will also assume that the engine failure occurs at a height which will kill you. It's not so much critical steps, it's critical outcomes. The single most critical outcome is to preserve, or regain, rotor RPM. What steps are needed to do this will depend on what the aircraft is doing ...


23

Many helicopters have more than one engine driving the rotor system. On those, losing an engine is probably less serious than it would be in a single-engine craft. All helicopters that I'm aware of are capable of autorotation. In an autorotation, the pilot uses the air rushing up through the rotor disk to keep the blades spinning. This involves changing ...


22

It's been a few decades since I crewed CH-46s, but the situation you're describing is called a de-sync and it's a catastrophic failure. The forward and aft rotors are linked by a driveshaft that drives the forward transmission and synchronizes the rotors. In a de-sync the intermeshed rotors will collide and the aircraft will tear itself to pieces. Also, ...


17

That drone has fixed-pitch rotors, and that pitch is optimized for thrust, not for autorotation. In the absence of power, those rotors won't autorotate. They will stop rotating 'in the right way' and then start windmilling in the opposite sense. That windmilling will cause drag and some deceleration of the fall, but not of the same magnitude as an ...


14

If a single motor fails, it's not unsafe (supposedly). The 184 is technically an X-8 multi-rotor, meaning that it has four points of thrust, each consisting of two motor-propellers, coaxially aligned—one “tractor” propeller and one “pusher.” This means that if any one of the motors dies, or a propeller disintegrates, the aircraft won’t flip and crash to the ...


13

According to https://en.wikipedia.org/wiki/NOTAR the NOTAR fan is driven by the main rotor transmission. This will ensure maneuverability during autorotation.


13

Highly improbable. If you've ever seen how much a washing machine can shake with a little imbalance in the laundry, at a relatively low energy spin, imagine the destructive forces that would be experienced by the imbalances in your theoretical rotors. Even if your missing blade manages to get away without causing impact damage to the other blades, there is ...


11

Simple answer. No. A drone with fixed wing propellers such as the one you describe can not autorotate. For autorotation to work the pitch of the blades needs to be variable. At the instant of engine failure, the main rotor blades are producing lift and thrust from their angle of attack and velocity. By immediately lowering collective pitch, which must be ...


11

It's entirely possible. Attitude control works the same way during autorotation as it does during normal powered flight. It's a good thing, too... during an autorotation you want to target your descent toward a suitable landing spot :-) To (say) roll right, moving the cyclic causes the swashplate to move in such a way that the rotor blade's pitch (angle of ...


11

What you're looking for is the height/velocity curve, some times called the 'dead man's curve'. This shows the altitude and speed requirements for a safe autorotation, plus the height and altitude conditions under which an autorotation is probably not possible. A lot of variables go into this, and the h/v curve is specific to the particular helicopter, and ...


10

This seems to be a hot topic - in principle, the V-22 should be able to fly and land in autorotation, but tests so far did not demonstrate this. The manufacturer's position is that autorotation was never part of the specification. What it comes down to is the inertia of the rotating parts relative to the aircraft's mass. The requirement to fold the rotors ...


9

Yes and yes. A certification requirement of helicopters with powered controls is that they have a manual reversion so that control can be maintained in the event of a power failure. However, the controls can be really heavy with no power and accidents have occurred when hydraulics have failed at critical moments or pilots have lifted off with hydraulics ...


9

It would be impossible. A rotor blade that has lost a large segment, or entire blade of a main rotor, would be so badly out of balance that it would immediately self destruct.


9

There are three good reasons to avoid Vertical Autorotation. First, Vertical Autorotation is way more likely to lead to a Vortex Ring condition where the air exiting the rotor disk gets recirculated back through the rotor disk. The recirculated air in the Vortex Ring then limits the amount of airflow/energy available for conversion to Rotor Disk rotational ...


9

Forgetting THEORY... a vertical autorotation IS possible and can be accomplished safely. To answer this question put to me by my Co-pilot that day in Vietnam, I took our H-Model Huey up to 5,000' and confirmed hover. I lowered the collective and chopped the throttle to split the needles and monitored rotor RPM to ensure no over-speed while keeping the cyclic ...


8

As a helicopter pilot, I've never made a water based landing, so I'm not speaking directly from experience, only from my training, but there are a couple things that are missed in the discussion here that I would certainly worry about. If I had a real engine failure, and was forced to perform an auto-rotation, in all likelihood, I would not end the auto-...


8

That is a very broad question and covers many topics, but I will try to answer as best I can and not miss anything. A quick note on the wings. Adding wings as a safety aspect to the aircraft kinda defeats the purpose of an autogyro. Would it survive to a rotor destruction? The likelihood of an autogyro surviving rotor destruction is extremely remote. ...


8

On the Chinook, the sprag clutches that allow the drive system to freewheel when an engine fails are between each engine's step-down transmission and the "combining transmission" that receives torque from each engine and sends it to the front and rear rotor transmissions. This means that the entire drive line between the rotors always remains engaged and in ...


7

In general, regardless of the number of blades, the more blade inertia, relative to blade area, the better for autorotation safety because the inertia buys you more time to establish the autorotative glide before blade stall when power is removed, and more time to settle into a landing at the end of the glide. The downside is more sluggish response to power ...


6

During an auto-rotation, you don't need torque compensation at all. Those vertical stabilizers are more than enough. Autogyros fly in auto-rotation all the time, and they don't need any torque compensating device, because in this type of aircraft the rotor is not powered by an onboard engine, but rotates freely, powered by the relative wind. In the absence ...


6

There is nothing that prevents tilt rotors from performing an autorotational landing, in theory. AugustaWestland AW 609 has already demonstrated this. The Bell XV-3 also did this. However, V22 has not demonstrated autorotation in any practical sense. The descent rate is too high for safe landing. The failure of V 22 to autorotate is due to the high wing ...


6

I am a career helicopter pilot who enjoys watching the development of drone technology. I can tell you for certain that this aircraft is incapable of autorotation. A parachute would be it's best option for pure simplicity. This would not guarantee a safe landing, just avoid a 'splat'. It is very apparent to me that the number one challenge of the drone ...


6

It seems that you already understand what an autorotation is but for the benefit of other readers, I'll recap what the flare is all about. There are two really critical parts of an autorotation. The entry and the flare. If you get the entry wrong, then there is no autorotation. You become a passenger all the way to the scene of the crash. If you get ...


6

You just fly your profile. Initially its with an instructor, but eventually you move on to training by yourself/copilot. You can practice full autos (to a landing), but some airframes practice to a hover or in early stages. In the TH-57B (Bell 206), you can take it a full power-off landing during training since it is light enough. However, moving up to the ...


6

Go back to Estes rocket days. There is a whole class of competition rockets known as "heliroc" or helicopter recovery. These ascend like a conventional rocket, in a vertical(ish) path and fin stabilized; at (or near) apogee, they release a rotor by some means and the rotor spontaneously begins to autorotate, often giving a lower descent rate than a ...


5

There's one major difference between a coaxial helicopter and a conventional single main rotor -- single tail rotor helicopter during autorotation: yaw control. A conventional helicopter has a main rotor which produces a torque. The tail rotor thrust, applied at the end of the tail boom, provides a counter-acting "anti-torque" to keep the helicopter ...


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