Differences

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--- aircraft:how_to_fly_a_helicopter [2020/10/08 10:01] – [Vertical Landing] jh
+++ aircraft:how_to_fly_a_helicopter [2020/10/08 16:49] (current) – [Hover] jh
@@ Line 77: / Line 77: @@
 So the typical attitude for a stationary hover is a bit nose up and slightly rolled to the left.
+{{ :aircraft:ec135_hover.jpg |}}
 ===== Standard Takeoff =====
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 During this phase it is important to maintain a small descent rate. Otherwise the rotor downwash will circle around the rotor and the rotor will loose a lot of lift causing a very high rate of descent. In this vortex ring state we're pretty much just a falling object. If you find yourself descending vertically very rapidly you will probably not be able to recover from it by just pulling more collective input. Instead you have to push the cyclic forward to bring the nose down and pull collective. That will push the downwash to the side and as you keep falling the rotor will no longer inject its own downwash.  It will gain lift again and you can pull up from the dive to fully recover.
+===== Autorotation =====
+When the engine(s) of a helicopter quit the rotor shaft mechanically disconnects from the engine driveshaft(s) because of the freewheel so that the rotor can keep spinning even if the engine stops.
+From that point forward the pilot has to change the collective pitch input in such a way that the rotor speed is maintained within limits. Raising the collective will cause the rotor RPM to drop. Lowering the collective increases the rotor speed. During the autorotation the helicopter constantly looses energy in form of friction or drag. Because of that we need to trade in either aircraft speed or altitude to gain rotor speed.
+When we are flying fast and an autorotation (short "auto") happens we can first trade our excess speed and even maintain or gain altitude by reducing the collective lever slightly and pitching the nose up with the cyclic stick.
+Once we decelerated to around 80 to 70 knots we decrease the collective input and start our glide towards the landing spot.
+When we are slower than that we first have to lower the collective and enter a dive to pick up airspeed before we can gently pull up.
+Depending on the helicopter size we aim for 60 to 70 knots indicated airspeed during the autorotation.
+We have to adjust the collective to maintain the rotor speed and use the cyclic controls to adjust the flight path.
+Find a location where you can land at. A professional pilot really doesn't need a lot of space but if you are still practicing then the entire airport area can be your landing spot.
+  * Use collective lever to control the rotor speed. Try to maintain 100% RPM at all time.
+  * Use cyclic pitch to control the airspeed
+  * Use cyclic roll to steer towards the landing spot.
+The approach during an auto may be steeper than you are used to, maintain your 60-70 knots airspeed until you are close to the ground. Then pitch up for the flare.
+  * Add aft cyclic pitch input to lift the nose up. This causes the rotor speed to increase.
+  * At the same time increase the collective slightly to arrest the descent rate.
+From here you can take use different strategies.
+A) On a hard surface or on a flat grass surface you can keep the helicopter at a level attitude and touch down using the collective input. This is much easier and safer but it can damage your skids when you skid down the runway. When the terrain is rough you could potentially flip over, which is not good. During the last phase and particularly on the ground try to keep the nose pointing straight ahead with your pedals.
+B) Reduce the forward speed close to zero before touching down. This requires a nose high attitude when you are close to the ground until the airspeed has dropped so much that the rotor speed decreases rapidly. You only have a few seconds to bring the nose down to a level attitude and touch down using collective inputs before the lift is getting too low and you'll be forced to touch down. During the round out and flare you are running the risk of a tail strike because of the nose high attitude so don't do this maneuver too close to the ground. Using the replay you can judge how close you were to a tailstrike later on.