New UK AICs, Helicopter Safety Related Topics.

[ShyTorque]

There are two new "Pink" AICs, (P 316/2019 and P 317/2019). Both discuss topics highly relevant to helicopter pilots and both previously discussed on this forum.

Here: NATS | AIS - Home (http://www.nats-uk.ead-it.com/public/index.php%3Foption=com_content&task=blogcategory&id=161&Itemid=58.html)

[RVDT]

From one who is no longer "young" enough to "know everything" - in aviation and in particular helicopters it pays to
"learn from the mistakes of others as you will not live long enough to make them all yourself" - Eleanor Roosevelt

[jellycopter]

The AIC relating to Servo Transparency (Jack Stall) quotes Airbus stating that 'Density Altitude' effects the likelihood of encountering the phenomenon. The CAA AIC goes further and states 'high density altitude' indicating that the risk is greater, the higher the aircraft.

If the air is less dense as altitude increases, how can Servo Transparency (caused by aerodynamic control loads) be more likely? Discuss.

JJ

[ApolloHeli]

The AIC relating to Servo Transparency (Jack Stall) quotes Airbus stating that 'Density Altitude' effects the likelihood of encountering the phenomenon. The CAA AIC goes further and states 'high density altitude' indicating that the risk is greater, the higher the aircraft.

If the air is less dense as altitude increases, how can Servo Transparency (caused by aerodynamic control loads) be more likely? Discuss.

JJ

Nothing but an educated assumption here; as density decreases, blade pitch will need to be increased to maintain a given flight condition (say 100kt cruise) so for a causal manoeuvre (usually a sharpish turn or pitch up), the severity of the manoeuvre needn't be as high to produce the same flight control loads as the collective pitch setting is already higher.

[ShyTorque]

Same effect as a greater mass.

[jellycopter]

Same effect as a greater mass.
I'm not so sure that's right. If weight is increased, then sure, collective pitch angle has to increase to produce the necessary lift. Accordingly, aerodynamic load increases and servo transparency can ensue.

Stay with me for a minute; hypothetically, if the aircraft were to be climbed to an infinite altitude, i.e. into space. There would be no aerodynamic load so no servo transparency.

I know retreating blade stall is exacerbated by increased density altitude, but Servo Transparency? I've yet to be convinced.

JJ


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[ShyTorque]

It's now Christmas Eve, my family have begun arriving with the grand kids and I'm not getting deeper into a discussion about work..

...I will hopefully be getting deep into a G&T any minute.

Have fun! ;)

[jellycopter]

Fair point! Enjoy!

[Ascend Charlie]

Jelly, by your logic there would also be no drag, so the chopper could fly at the speed of heat.

[Hot and Hi]

There are two new "Pink" AICs, (P 316/2019 and P 317/2019). Both discuss topics highly relevant to helicopter pilots and both previously discussed on this forum.

Here: NATS | AIS - Home (http://www.nats-uk.ead-it.com/public/index.php%3Foption=com_content&task=blogcategory&id=161&Itemid=58.html)
Thanks for sharing this link. The AIC on degraded visibility is particularly well written. While already it would be difficult to fault the authors on any given argument presented, the decidedly deliberate style of writing, avoiding to limit itself to only to indisputable common place statements, is particularly refreshing and adds real value.

I find it much more stimulating to follow such “it can be argued” lines of thought than the usual pontificating that takes place on such topics.

[JimEli]

“...flight tests data indicate that servo transparency could not be encountered if the collective is less than 50% raised.”