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Fly_Guy

Does Anyone Know The Reason For "maximum Rate Of Climb" In A 407 Or 214?

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Hi All,

 

Just wondering if anyone has any reference material, or can shed some light on the reason for "Maximum Rate Of Climb" in the 407 and 214?

 

It presents an unsafe cyclic displacement? Or could it be because it puts the aircraft in an unsafe position in the event of an engine failure?

 

Curious to hear the reasoning behind it.

 

Thanks guys,

 

 

Fly_Guy

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214 limit is supposedly because of engine failure, if you were say... climbing at 5000-6000FPM and had a power failure momentum would continue to carry you upwards for long enough that the RRPM would decay below a critical point before actual autorotation was established.

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Don't know about the 214 but it's to do with fuselage attitude on the 407 which has a damped ASI, so you are getting information after the event. The max rate of climb ensures that you have some sort of correct attitude if the engine quits.

 

Phil

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Yup, this was the explanation from Bell I was given for the 407 also...

 

 

214 limit is supposedly because of engine failure, if you were say... climbing at 5000-6000FPM and had a power failure momentum would continue to carry you upwards for long enough that the RRPM would decay below a critical point before actual autorotation was established.

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I was told years ago that the Skycrane had a similar limitation because it had such a powerful rate of climb that RRPM would decay to the point of no recovery before you could initiate an auto rotative descent in the event of a total engine failure just as Nobul said about the 214.

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Nope...no such limitation on the cranes, but it is mentioned under normal operations in the RFM.... common sense and experience dictates that we pretty much restrict our rate of climb depending on airspeed.

And in my 214 days...I took that restriction very seriously as it is a single engine aircraft.

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Hello All, Just wanted to say that all response's sound good. As Helilog said, my experience on Crane, That was not an issue, maybe on the back burner yes. But my experience on 214B, one year during yearly recurrunt training, we played with maxium rate of climbs, up a slope simulating a heli-logging turn. power was rolled off, yes there was a big decay, but I learned was that was key was , turning left was your friend. we actually spent about 45 mins playing with this.

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Hello All, Just wanted to say that all response's sound good. As Helilog said, my experience on Crane, That was not an issue, maybe on the back burner yes. But my experience on 214B, one year during yearly recurrunt training, we played with maxium rate of climbs, up a slope simulating a heli-logging turn. power was rolled off, yes there was a big decay, but I learned was that was key was , turning left was your friend. we actually spent about 45 mins playing with this.

 

Yep ..... if you just pushed the stick forward ..... you would have lots of rotor decay. But if you are logging and going up the side of a mountain who would do that anyways?

 

Chop the throttle and turn left ... keep the disc loaded and not only do you keep your rpm but you gain another 300 feet or so and by the time you get turned 180 degrees then you are nicely established in an autorotation and pointed towards the center of the valley. You actually pull back on the stick a bit to make the turn so the disc is always loaded.

 

It would probably work the same turning right but if you are in the left seat .... that is the natural way to turn.

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Fly_Guy,

 

I can't speak to the 214 but the rate of climb limitation on the 407 is a result of, like you said, cyclic position and it is not an autorotation issue. This is my understanding and best explanation of the issue.

 

During the 407 certification process, one of the tests involved cyclic position during specific phases of flight. There is an allowable range within the full travel range in which the cyclic must remain, think of it as a box within a box. During rates of climb above 2000 FPM, the cyclic had to be moved aft outside the allowed range to maintain level flight and this required a limitation to be imposed.

 

The cause of the aft cyclic input during rates of climb over 2000 FPM is due to a loss of smooth airflow over the horizontal stabilizers. In spite of the leading edge slots in place to maximize the stall angle, the downwash from the rotor system and airflow from such a high climb speed causes the stabilizers to stall. This decrease of downforce produced by the horizontal stabilizers combined with the increased downforce on the forward fuselage causes a nose down pitching and aft cyclic pilot input.

 

Keep in mind that this limitation is measured by the VSI which reads pressure change and not direct airflow over the fuselage.

 

Hope that helps.

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