747 Less thrust = Loss of Lift???
John T, I suspect it depends on the wing/engine interface. Back during the original development of the 767, I was a fresh faced young engineering working nacelle aero - and at the time it was my understanding that we only needed the strake for the engine out condition.
Since then, engines have gotten progressively larger in diameter and more closely coupled with the wing (the 737 being an extreme example of that). So you may well be correct that it now goes beyond the engine out scenario.
On the 747-8, the need for the strake was identified very early on, and there was a pretty good fight between the aero types and where they wanted it to go, and the mechanical types that actually had to make the location workable
Since then, engines have gotten progressively larger in diameter and more closely coupled with the wing (the 737 being an extreme example of that). So you may well be correct that it now goes beyond the engine out scenario.
On the 747-8, the need for the strake was identified very early on, and there was a pretty good fight between the aero types and where they wanted it to go, and the mechanical types that actually had to make the location workable
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A Pulled Chain; Making Fun? I Think Not
Engineer, not transport driver, here...
Moderator John commented:"
"I recall, years ago during the early 733 days in Australia, a CASA airworthiness engineer asking me over coffee whether I would be concerned taking a 733 minus a chine without any engineering consideration. I think my ashen face gave him my answer ... (emphasis added) it transpired that a local operator (the other one - not mine) had done just this a few days prior ... CASA had, quite appropriately, taken a dim view of the matter ..."
I would take more than a dim view of this. I would not start the SOB in that condition, let alone fly with it. I'd like to think John is making fun or yanking our chains a bit here, but he does not do that. CASA's 'dim view,' must be the understatement of the year; they should have grounded the entire fleet where located, until complete inspections were done. This falls into the 'you've got to be kidding me,' class, except that again, Moderator John does not do that. CASA nailed it; a seriously stupid practice. I have to wonder if there was an investigation and/or report covering the circumstances. John?? If so, can you dredge up a link? Thanks...
Moderator John commented:"
"I recall, years ago during the early 733 days in Australia, a CASA airworthiness engineer asking me over coffee whether I would be concerned taking a 733 minus a chine without any engineering consideration. I think my ashen face gave him my answer ... (emphasis added) it transpired that a local operator (the other one - not mine) had done just this a few days prior ... CASA had, quite appropriately, taken a dim view of the matter ..."
I would take more than a dim view of this. I would not start the SOB in that condition, let alone fly with it. I'd like to think John is making fun or yanking our chains a bit here, but he does not do that. CASA's 'dim view,' must be the understatement of the year; they should have grounded the entire fleet where located, until complete inspections were done. This falls into the 'you've got to be kidding me,' class, except that again, Moderator John does not do that. CASA nailed it; a seriously stupid practice. I have to wonder if there was an investigation and/or report covering the circumstances. John?? If so, can you dredge up a link? Thanks...
Last edited by No Fly Zone; 31st Aug 2015 at 08:54. Reason: delete incorrect word, typos
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looking at the list it appears that things that cause nose up pitch help and things that cause nose down don't!
Not really a surprise then that when you have to increase tail downforce you lose manoeuvre margin.
Not really a surprise then that when you have to increase tail downforce you lose manoeuvre margin.
Moderator
I suspect it depends on the wing/engine interface.
Indeed.
Presuming you work where I presume you do, I shall give due weight to your comments.
A great value of PPRuNe is the wealth of serious knowledge which is available from folks such as your goodself.
they should have grounded the entire fleet where located
As I understood the tale, it was an inappropriate one-off during the early post-introduction days of the model and not at all typical of the operation .. which was every bit as tight as that at the other mob for which I flew.
Interestingly, I don't recall any discussion of the chines during my endorsement on the Type around the same time. I guess the importance to the performance numbers hadn't filtered down to appropriate training levels within the system ?
Indeed.
Presuming you work where I presume you do, I shall give due weight to your comments.
A great value of PPRuNe is the wealth of serious knowledge which is available from folks such as your goodself.
they should have grounded the entire fleet where located
As I understood the tale, it was an inappropriate one-off during the early post-introduction days of the model and not at all typical of the operation .. which was every bit as tight as that at the other mob for which I flew.
Interestingly, I don't recall any discussion of the chines during my endorsement on the Type around the same time. I guess the importance to the performance numbers hadn't filtered down to appropriate training levels within the system ?
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Aircraft with their engines "underslung " have the advantage, normally, of more power tends to give a climb ( which may be compensated by the A/P). Looking at the traces of AF447, when power was reduced to Flight Idle briefly, the nose came down by a few degrees. (A/P was OFF) The aircraft may have been in an unrecognised stall at that time.
Even simple gliders tended to be wiinch launched from under the Pilot's seat . Or aerotowed from the nose. In each case this was to get the better performance.
Perhaps something like the 4 knots mentioned may apply to other aircraft with underslung engines, depending on where the engines are located in relation to the " Vertical C of G". (Usually one only considers the Fore and Aft C of G.)
LT
Even simple gliders tended to be wiinch launched from under the Pilot's seat . Or aerotowed from the nose. In each case this was to get the better performance.
Perhaps something like the 4 knots mentioned may apply to other aircraft with underslung engines, depending on where the engines are located in relation to the " Vertical C of G". (Usually one only considers the Fore and Aft C of G.)
LT
Last edited by Linktrained; 31st Aug 2015 at 18:24.
