BAe146QT From United Kingdom, joined Sep 2006, 989 posts, RR: 0 Posted (4 months 1 day 23 hours ago) and read 3265 times:
Hello all! Quick question since my search-fu is clearly rubbish and I haven't found anything definitive.
What's the usual climb profile, from runway to 33,000ft for a 757-200 with an average load, please? For example, 3000FPM to 10k, followed by 2000FPM up to 24k...etc. Or whatever. Be as generic as you like.
Let me know if the question is too vague, but please assume 29.92, negligible winds, and an 80% load.
And if you're a 757 driver, please feel free to share your experiences of other circumstances.
DashTrash From United States of America, joined Aug 2006, 1164 posts, RR: 2 Reply 1, posted (4 months 1 day 22 hours ago) and read 3231 times:
Climb profiles are predicated on airspeeds / mach numbers at the transition, not on vertical speed. I imagine a 75 driver will come on here and say for sure, but I something for MSFS purposes could be 250kt til 10K, then 300kt transition to .7M all the way up.
Climb profiles are predicated on airspeeds / mach numbers at the transition, not on vertical speed. I imagine a 75 driver will come on here and say for sure, but I something for MSFS purposes could be 250kt til 10K, then 300kt transition to .7M all the way up.
Vertical speed will always vary, depending on weight, temperature and density altitude but the above profile is not correct.
In the US we are limited to 250KIAS below 10,000 ft, other countries will allow us to accelerate to our normal climb speed which is closer to 310 knots, sometimes as high as 330 transitioning to .8 Mach during the climb.
The best contribution to safety is a competent Pilot.
mercure1 From French Polynesia, joined Jul 2008, 326 posts, RR: 3 Reply 3, posted (4 months 1 day 14 hours ago) and read 3031 times:
Quoting BAe146QT (Thread starter): What's the usual climb profile, from runway to 33,000ft for a 757-200 with an average load, please? For example, 3000FPM to 10k, followed by 2000FPM up to 24k...etc. Or whatever. Be as generic as you like.
For a 757-200 RB211-535E4 @ 100t TOM and ISA+10, using a normal 250kt to 10k, 300kt to M.80 crossover profile up to 35k. After going to CLB power, accelerating to 250kts by 3000ft, the RoC (rate of climb) is ~ 3200fpm
At 10k, its down to around 2900fpm at 250kts
Accelerating at 500fpm to 300kts by 11k the RoC is ~ 2800fpm
by 15k RoC is ~ around 2500fpm
by 20k RoC is ~ 2000fpm
by 25k RoC is ~ 1600fpm
by 30k RoC is ~ 1200fpm
by 35k RoC is ~ 1000fpm*
*This should all take about 118nm, 2.5t of fuel, and around 19min since liftoff.
DashTrash From United States of America, joined Aug 2006, 1164 posts, RR: 2 Reply 4, posted (4 months 1 day 13 hours ago) and read 2988 times:
Quoting Max Q (Reply 2):
In the US we are limited to 250KIAS below 10,000 ft, other countries will allow us to accelerate to our normal climb speed which is closer to 310 knots, sometimes as high as 330 transitioning to .8 Mach during the climb.
330 to .8 in a 757? I thought your index usually had you around .76 in cruise?
Max Q From United States of America, joined May 2001, 2616 posts, RR: 19 Reply 5, posted (4 months 1 day 11 hours ago) and read 2949 times:
.76 is too slow, generally we are cruising around .8 Mach. Our Cost index's are not fixed but vary depending on the mission.
If you are returning from Berlin in the winter for example you would probably be close to cost index 0 to get the absolute maximum range out of the Aircraft but that will be pretty close to .8 slowing later in the flight as you get lighter.
Remember with strong headwinds it doesn't pay to go too slow as you spend so much longer flying into the wind burning more fuel as a result.
If we are in a hurry trying to make up time 330 knots plus to .83 will be used if necessary.
The best contribution to safety is a competent Pilot.
I had no idea the airplane was that fast. I get a little lost on the whole cost index thing since my jet exposure is limited to bizjets. Our dispatch took care of all the jazz, but rarely had us changing mach numbers.
BAe146QT From United Kingdom, joined Sep 2006, 989 posts, RR: 0 Reply 7, posted (4 months 1 day ago) and read 2708 times:
Thanks very much guys, especially for indulging a sim flyer in Tech/Ops.
Quoting DashTrash (Reply 1): Climb profiles are predicated on airspeeds / mach numbers at the transition, not on vertical speed...something for MSFS purposes
Heh, busted - that's exactly what I wanted it for!
Quoting Max Q (Reply 2): Vertical speed will always vary, depending on weight, temperature and density altitude but the above profile is not correct.
Given that I'm a chicken and so usually 'fly' fair weather, the thing I notice the most is the weight factor (mostly from the fuel on long flights). But even then it's no slouch as you obviously know. A brief search shows a T:W ratio at MTOW of 2.93 which is...extraordinary. I'm guessing that's why they're used as the Vomit Comet...? I'd love to know if Boeing ever took an empty one with minimal fuel and tested what the maximum climb performance from sea level was.
Quoting mercure1 (Reply 3):
For a 757-200 RB211-535E4 @ 100t TOM and ISA+10, using a normal 250kt to 10k, 300kt to M.80 crossover profile up to 35k. After going to CLB power, accelerating to 250kts by 3000ft, the RoC (rate of climb) is ~ 3200fpm
At 10k, its down to around 2900fpm at 250kts
Accelerating at 500fpm to 300kts by 11k the RoC is ~ 2800fpm
by 15k RoC is ~ around 2500fpm
by 20k RoC is ~ 2000fpm
by 25k RoC is ~ 1600fpm
by 30k RoC is ~ 1200fpm
by 35k RoC is ~ 1000fpm*
*This should all take about 118nm, 2.5t of fuel, and around 19min since liftoff.
That's actually not far off how I've been flying it, (confirmed by my takeoff from Gatwick to Malta about half an hour ago). Essentially chasing the speeds, with the climb rate being dictated by that. The aircraft I'm using (Project OpenSky 757-200 w/ RB211s) lists in the kneeboard what your cruise speed should be at various altitudes, and so I figured it must be dynamic.
Once again, thank you for your responses. I'll never fly a real one, but it's good to have info that makes the sim more enjoyable.
Max Q From United States of America, joined May 2001, 2616 posts, RR: 19 Reply 8, posted (4 months 21 hours ago) and read 2636 times:
Quoting DashTrash (Reply 6):
I had no idea the airplane was that fast. I get a little lost on the whole cost index thing since my jet exposure is limited to bizjets. Our dispatch took care of all the jazz, but rarely had us changing mach numbers.
It's ok, but it doesn't compare with the great old B727, that was a fast Aircraft which we could cruise at .86 comfortably
and higher if you didn't care about the fuel !
The best contribution to safety is a competent Pilot.
OldAeroGuy From United States of America, joined Dec 2004, 3141 posts, RR: 66 Reply 9, posted (4 months 20 hours ago) and read 2602 times:
Quoting DashTrash (Reply 6): I had no idea the airplane was that fast.
Yes, the 757 was designed to cruise at 0.80M
Quoting Max Q (Reply 8): It's ok, but it doesn't compare with the great old B727, that was a fast Aircraft which we could cruise at .86 comfortably
and higher if you didn't care about the fuel !
Of course in the 727's prime, fuel was $0.10USD per gallon.
Airplane design is easy, the difficulty is getting them to fly - Barnes Wallis
DashTrash From United States of America, joined Aug 2006, 1164 posts, RR: 2 Reply 10, posted (4 months 14 hours ago) and read 2514 times:
Quoting Max Q (Reply 8):
It's ok, but it doesn't compare with the great old B727, that was a fast Aircraft which we could cruise at .86 comfortably
and higher if you didn't care about the fuel !
....and the noise too from what I've been told. Fast is fun, however. I got very spoiled flying the X.
BAe146QT From United Kingdom, joined Sep 2006, 989 posts, RR: 0 Reply 12, posted (3 months 2 weeks 4 days 22 hours ago) and read 1768 times:
Quoting Max Q (Reply 11): Yes, it was noisy.
I ferried one unpressurized once, that was unbelievably loud.
We had to shout at each other in the Cockpit.
Can I ask why you had to do that? Was it a pressurisation fault that needed to go back to base to be fixed?
BAe146QT From United Kingdom, joined Sep 2006, 989 posts, RR: 0 Reply 14, posted (3 months 2 weeks 3 days 23 hours ago) and read 1548 times:
Yikes! In the tail dome?
Another question about that if you don't mind; Did you keep it below 10,000' or did you go higher than that and stay on supplementary oxygen? And if you stayed down low, what sort of ride was it?
(I know that there's a maximum altitude that you can go to even on the masks, because of physical limitations of the chest muscles, but danged if I can remember what it is. 30,000'?)
Max Q From United States of America, joined May 2001, 2616 posts, RR: 19 Reply 15, posted (3 months 2 weeks 3 days 20 hours ago) and read 1493 times:
Quoting BAe146QT (Reply 14):
Another question about that if you don't mind; Did you keep it below 10,000' or did you go higher than that and stay on supplementary oxygen? And if you stayed down low, what sort of ride was it?
Funny you asked that, we started at 10,000 feet, then, after a while decided to take it a little higher, perhaps 14000' we though, however, as we started to climb we got the Cabin Altitude Warning Horn of course.
So we went back down to 10,000, good thing too as we had all forgotten that the 'rubber jungle' would fall automatically at a cabin altitude of 140000'
This is when all the oxygen masks in the Cabin deploy. It would have been a little hard to explain on arrival..
The best contribution to safety is a competent Pilot.
vikkyvik From United States of America, joined Jul 2003, 6516 posts, RR: 29 Reply 16, posted (3 months 2 weeks 3 days 19 hours ago) and read 1461 times:
Quoting BAe146QT (Reply 7): But even then it's no slouch as you obviously know. A brief search shows a T:W ratio at MTOW of 2.93 which is...extraordinary. I'm guessing that's why they're used as the Vomit Comet...?
I'm assuming 2.93 is the weight-to-thrust ratio, rather than thrust-to-weight. Even fighter aircraft don't have T/W ratios that high!
For the Vomit Comet, if you're referring to the NASA airplanes, they used KC-135s for most of the time, and a few years ago switched to C-9Bs (DC-9s).
BAe146QT From United Kingdom, joined Sep 2006, 989 posts, RR: 0 Reply 18, posted (3 months 2 weeks 2 days 22 hours ago) and read 1313 times:
Thank you vikkyvik - yes I got that the wrong way around. And I thought that the 757 was the weapon of choice for the Vomit Comet, so I guess that'll learn me to not listen to the media.
Anyway, it you'll indulge me, I tried to fly a simulated 757-200 properly earlier.
Route: KMIA-KBOS (1080NM direct)
Load: 202 Spring-time Pax, full cargo, 45% fuel.
WX: Wind 270@5Kts until 18000' then 270@25kts.
Does that look right? I get the impression that the motors on my sim bird are a little more powerful and durable than the real ones?
I took into account engine load - I wasn't maxing them out and wasn't ignoring fuel burn, which is easy to do in a sim. I was being conservative. So it looks like a steep bell curve with a shallow peak? Either way, I reckon this is all far more complicated than people might realise.
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