What causes a helicopter to shudder when ETL is lost?
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Dash1B,
Speaking as one arrogant condescending Bastard, I can assure you that you have finally come to where I was several pages back. Thanks, next time try to get there before you write the return post!
Quick Release, The post I made answering the original question had the exact answer, as well as providing two research web sites with illustrations and data. How did that miss your exactling eye?
Gentlemen, I find it amusing when a question is asked, it is then anserwed, and then several student pilots read their text books back to refute the answer. Specifically, when Crab or JimL or any of the truly experienced experts who frequent this site post an answer, they do so not by reading the "Dick and Jane" texts that students get, but by being in that rare group who actually did the work that helped write those texts. I will flatter myself and say that I am in that group. Call that arrogant if you wish. Or call that informed. Point of view, I think.
Speaking as one arrogant condescending Bastard, I can assure you that you have finally come to where I was several pages back. Thanks, next time try to get there before you write the return post!
Quick Release, The post I made answering the original question had the exact answer, as well as providing two research web sites with illustrations and data. How did that miss your exactling eye?
Gentlemen, I find it amusing when a question is asked, it is then anserwed, and then several student pilots read their text books back to refute the answer. Specifically, when Crab or JimL or any of the truly experienced experts who frequent this site post an answer, they do so not by reading the "Dick and Jane" texts that students get, but by being in that rare group who actually did the work that helped write those texts. I will flatter myself and say that I am in that group. Call that arrogant if you wish. Or call that informed. Point of view, I think.
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Nicklappos
I do stand corrected, no i didnt read many posts and did miss the important ones (obveousley), i only offered an enalergy instead, be it a bad one. I wll call it a learning curve re: posting and will only offer technical fact in future. Now can we move on?
I do stand corrected, no i didnt read many posts and did miss the important ones (obveousley), i only offered an enalergy instead, be it a bad one. I wll call it a learning curve re: posting and will only offer technical fact in future. Now can we move on?
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Mr. Lappos:
Telling a student who is simply trying reconcile your explanation with the flight school textbook answer that he is "spouting gobbledegook" is condescending and unconstructive.
Every student reserves the right to question and not accept answers on blind faith, even those coming from household names with monolithic credentials.
You made two points:
1. ETL transition vibrations are due to BVI. Thank you for setting us straight, unfortunate that the textbook is so misleading.
2. There is no blade slap because the velocities aren't high enough for transsonic shock formation. While true, this did not answer the question, there are still several other mechanisms present to generate blade slap at subsonic velocities. Mr. Crab helped shed some light on this by mentioning the angle dependency, thank you Mr. Crab.
Anyway, my name-calling was equally unconstructive, and I retract it.
-1B
Telling a student who is simply trying reconcile your explanation with the flight school textbook answer that he is "spouting gobbledegook" is condescending and unconstructive.
Every student reserves the right to question and not accept answers on blind faith, even those coming from household names with monolithic credentials.
You made two points:
1. ETL transition vibrations are due to BVI. Thank you for setting us straight, unfortunate that the textbook is so misleading.
2. There is no blade slap because the velocities aren't high enough for transsonic shock formation. While true, this did not answer the question, there are still several other mechanisms present to generate blade slap at subsonic velocities. Mr. Crab helped shed some light on this by mentioning the angle dependency, thank you Mr. Crab.
Anyway, my name-calling was equally unconstructive, and I retract it.
-1B
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Dash1B,
Thanks for that, your points were valid, and questions are always instructive!
Keep digging, please, just watch how you swing that shovel.
As a clarification, most BVI does involve increased noise. The classic blade "slap" that one hears when a Huey passes overhead is a transonic effect, while the muffled blade slap that one sometimes hear (hack writers sometimes say the "clatter of rotors") is just the subsonic flow disturbence. One helo I flew had a nagging muttering noise at 40 knots while at aft CG, the product of the BVI. Forward CG was fine, and if the aircraft was acelerating, the noise disappeared.
Thanks for that, your points were valid, and questions are always instructive!
Keep digging, please, just watch how you swing that shovel.
As a clarification, most BVI does involve increased noise. The classic blade "slap" that one hears when a Huey passes overhead is a transonic effect, while the muffled blade slap that one sometimes hear (hack writers sometimes say the "clatter of rotors") is just the subsonic flow disturbence. One helo I flew had a nagging muttering noise at 40 knots while at aft CG, the product of the BVI. Forward CG was fine, and if the aircraft was acelerating, the noise disappeared.
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Mr. Lappos:
Thanks for the further clarification. Sorry for crossing swords with you. We are fortunate that someone with your wealth of experience frequents these boards. I'd say Mr. Controller got his money's worth!
-1B
Thanks for the further clarification. Sorry for crossing swords with you. We are fortunate that someone with your wealth of experience frequents these boards. I'd say Mr. Controller got his money's worth!
-1B
Vibrations felt through ETL
Trying to find a conclusive answer as to the cause of the vibrations felt when moving through ETL.
They have been described as "vortices blowing off the blades" and " one blade traveling through clean air whilst the other blades are still in dirty air" Both seem rather simple answers to what I am sure is a more complex aerodynamic issue
Anyone able to enlighten me?
Barotrauma
They have been described as "vortices blowing off the blades" and " one blade traveling through clean air whilst the other blades are still in dirty air" Both seem rather simple answers to what I am sure is a more complex aerodynamic issue
Anyone able to enlighten me?
Barotrauma
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Already explored
Hi there,
I think this subject has been discussed in another forum with 45 replies... so hopefully one of them will strike a chord (no pun intended) with you.
I'm not sure how to post a hyperlink to the thread but go to the search function and type in 'vibrations' and 'ETL' and it will take you right there. (16 July 2005, I think)
(Maybe someone more computer savvy can post the link.)
Cheers
CB
I think this subject has been discussed in another forum with 45 replies... so hopefully one of them will strike a chord (no pun intended) with you.
I'm not sure how to post a hyperlink to the thread but go to the search function and type in 'vibrations' and 'ETL' and it will take you right there. (16 July 2005, I think)
(Maybe someone more computer savvy can post the link.)
Cheers
CB
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Telling a student who is simply trying reconcile your explanation with the flight school textbook answer that he is "spouting gobbledegook" is condescending and unconstructive.
Si
