June 24, 2011, 00:15:00 GMT
permalink Post: 6532637
<<
I'm guessing you mean rate of climb rather than IAS?
>>
<<No, I meant the airspeed you'd be flying at while climbing (post takeoff)>>
OK, then the answer to your Q's:
Also what was the typical climb speed
- At lift-off? About 200kts
- Once 240 kts is achieved? 240kts
- At minimum maneuvering speed at typical takeoff weight? Vla after takeoff was V2 until 15,000'. I.E. about 220kts
- At MTOGW? V2 didn't vary much by weight
Out of JFK we flew at Vmo once further than 12nms from the coast. Vmo=400kts IAS at low level.
Out of LHR overland the IAS restriction was 300kts until past the speed limit point early in the SID - much less draggy than 250kts and hence better climb rates. But you'd quickly be released to get to 400kts (barder's pole) where it was designed to be flown.
<<Why higher speed? That have to do with shockwaves and the resulting pressure distribution differences?>>
The flight envelope was bigger and more complex than subsonic types: it was developed in flight test and probably had many considerations involved. I think someone posted it earlier in this thread in graphical form (from the flight manual) if you want to see it. In practice, you had to be aware of three basic parameters - IAS, Mach and CG position (the CG "corridor"). Once understood, it wasn't that difficult to keep up with it...and the IAS and Machmeters had barber's poles handily programmed to show the limiting values (including, cleverly, max temp on the nose Tmo=127 degrees celcius).
Regarding climb rates - best ROC was at 400kts (MTOW) or 380kts (MLW). As speed reduced below that, drag increased and ROC reduced. At MTOW and 400kts you'd get about 4000fpm max dry power. At 250kts it was all noise and very few feet per minute - after noise abate procedures you had to lower the nose, just barely climb, and get IAS up toward min drag as soon as possible. With an engine failed go for 300kts minimum - Vmo as soon as you can.
<<shockwaves and the resulting pressure distribution differences>>
You had to avoid the "transonic" region due to these effects: maximum subsonic cruise was 0.95M due to the auto-stabilised flying controls become over-active as shockwaves started to "dance" around the airframe (usually asymmetrically). This calmed down by about 1.3M in the acceleration (when the intake ramps started to do their thing). To accelerate to 2.0M you needed reheat until 1.7M so you didn't hang around between 0.95M and 1.7M. FL260 was best for subsonic cruise because at that level 400kts IAS = 0.95M...
<<No, I meant the airspeed you'd be flying at while climbing (post takeoff)>>
OK, then the answer to your Q's:
Also what was the typical climb speed
- At lift-off? About 200kts
- Once 240 kts is achieved? 240kts
- At minimum maneuvering speed at typical takeoff weight? Vla after takeoff was V2 until 15,000'. I.E. about 220kts
- At MTOGW? V2 didn't vary much by weight
Out of JFK we flew at Vmo once further than 12nms from the coast. Vmo=400kts IAS at low level.
Out of LHR overland the IAS restriction was 300kts until past the speed limit point early in the SID - much less draggy than 250kts and hence better climb rates. But you'd quickly be released to get to 400kts (barder's pole) where it was designed to be flown.
<<Why higher speed? That have to do with shockwaves and the resulting pressure distribution differences?>>
The flight envelope was bigger and more complex than subsonic types: it was developed in flight test and probably had many considerations involved. I think someone posted it earlier in this thread in graphical form (from the flight manual) if you want to see it. In practice, you had to be aware of three basic parameters - IAS, Mach and CG position (the CG "corridor"). Once understood, it wasn't that difficult to keep up with it...and the IAS and Machmeters had barber's poles handily programmed to show the limiting values (including, cleverly, max temp on the nose Tmo=127 degrees celcius).
Regarding climb rates - best ROC was at 400kts (MTOW) or 380kts (MLW). As speed reduced below that, drag increased and ROC reduced. At MTOW and 400kts you'd get about 4000fpm max dry power. At 250kts it was all noise and very few feet per minute - after noise abate procedures you had to lower the nose, just barely climb, and get IAS up toward min drag as soon as possible. With an engine failed go for 300kts minimum - Vmo as soon as you can.
<<shockwaves and the resulting pressure distribution differences>>
You had to avoid the "transonic" region due to these effects: maximum subsonic cruise was 0.95M due to the auto-stabilised flying controls become over-active as shockwaves started to "dance" around the airframe (usually asymmetrically). This calmed down by about 1.3M in the acceleration (when the intake ramps started to do their thing). To accelerate to 2.0M you needed reheat until 1.7M so you didn't hang around between 0.95M and 1.7M. FL260 was best for subsonic cruise because at that level 400kts IAS = 0.95M...
Last edited by NW1; 24th June 2011 at 09:09 .
Subjects
Afterburner/Re-heat
C of G
Flight Envelope
IAS (Indicated Air Speed)
Intakes
JFK
LHR
Shockwave
V2
Vmo
Links are to this post in the relevant subject page so that this post can be seen in context.
Reply to this quoting this original post. You need to be logged in. Not available on closed threads.
June 25, 2022, 00:14:00 GMT
permalink Post: 11251293
Point taken GF, but it was discovered during development flying that that the Olympus 593 could be relit, given sufficient IAS, at almost any altitude within the normal flight envelope. The variable inlet would even be automatically scheduled, as a funcion of N1, in order to improve relight performance at lower Mach numbers. I certainly agree that you would decelerate and lose altitude fairly quickly under these conditions, however a multiple flame out was never experienced during the entire 34 years of Concorde flight testing and airline operation. There was, as a matter of interest an un-commanded deployment of a Concorde RAT AT MACH 2!! (The first indications of the event were when the cabin crew complained about 'a loud propeller sound under the rear cabin floor'. A quick scan of the F/E's panel revealed the truth of the matter). The aircraft landed at JFK without incident, and the RAT itself, apart from a very small leak on one of the hydraulic pumps, was more or less un-phased by the event. Although it sounds horrific, a prop rotating in a Mach 2 airstream, the IAS it 'felt' would be no more than 530 KTS at any time. The RAT was of course replaced before the aircraft flew back to LHR.
Not quite sure about your reference to the RAT on an F16 being Hydrazine powered; a Ram Air Turbine is just that, using the freely rotatting propellor to power hydraulics, electrics or both. Or do you mean the the F16 has an emergency power unit? Either way, it's fascinating stuff.
Yes, I do remember that the Germans used Hydrazine as a fuel during WW2: The father of one of our Concorde pilots was on an air raid to destroy one o the production plants there, this aviation business is such a small world.
Not quite sure about your reference to the RAT on an F16 being Hydrazine powered; a Ram Air Turbine is just that, using the freely rotatting propellor to power hydraulics, electrics or both. Or do you mean the the F16 has an emergency power unit? Either way, it's fascinating stuff.
Yes, I do remember that the Germans used Hydrazine as a fuel during WW2: The father of one of our Concorde pilots was on an air raid to destroy one o the production plants there, this aviation business is such a small world.
What I found interesting is that the AC generators would remain on-line at all; they drop instantaneously at subsonic speeds and the associated N2 rpm. I believe the hydraulics on the 747 will power flight controls down to a pretty low IAS.
Four engine flameout is a very unlikely event, unless one runs into a volcanic cloud.
Subjects
Boeing 747
Cabin Crew
Flameout
Flight Envelope
Hydraulic
Hydrazine
IAS (Indicated Air Speed)
Intakes
JFK
LHR
N1 (revolutions)
Olympus 593
RAT (Ram Air Turbine)
Relight
Links are to this post in the relevant subject page so that this post can be seen in context.
Reply to this quoting this original post. You need to be logged in. Not available on closed threads.