250 below 10000

[A Squared]

Forgive me if this has been covered in the preceding bazillion posts (cuz I haven't read them all), but I seem to remember hearing some whales departing DTW telling ATC that their climb speed would be 285. Was I dreaming this up? Not that it really changes anything in this 250/10000 discussion. Just curious, haven't been flying where they launch whales since '01.

Yeah, that's covered in the same reg.

91.117 (d) If the minimum safe airspeed for any particular operation is greater than the maximum speed prescribed in this section, the aircraft may be operated at that minimum speed.

 

[Resocha]

Forgive me if this has been covered in the preceding bazillion posts (cuz I haven't read them all), but I seem to remember hearing some whales departing DTW telling ATC that their climb speed would be 285. Was I dreaming this up? Not that it really changes anything in this 250/10000 discussion. Just curious, haven't been flying where they launch whales since '01.

We routinely climb out around 275-280 when we're really heavy, but that's in the classic 747. In the -400, maybe they're slightly faster as they have a slightly higher TOW.

 

[doublepsych]

We routinely climb out around 275-280 when we're really heavy, but that's in the classic 747. In the -400, maybe they're slightly faster as they have a slightly higher TOW.

Hey Resocha:

What kind of climb rate do you get at that speed when you're heavy? Having watched a few, it looks like a pretty shallow climb, until the thing gets up to speed...

 

[Resocha]

Deleted/duplicate

 

[Resocha]

Hey Resocha:

What kind of climb rate do you get at that speed when you're heavy? Having watched a few, it looks like a pretty shallow climb, until the thing gets up to speed...

Shortly after t/o with all the crap hanging out, at 800,000 pounds, we're getting nearly 1000 fpm, depending on ISA dev. We use a speed called Vf, which is a customized flap-retraction reference speed. At 780,000 pounds, Vf is 172. After we're cleaned up, we accelerate to Vf+100, so in that case we'd be climbing at 272 (rounded to 275). Once clean, the rate can pick up to 2500fpm or so. Out of 10,000, we accelerate to Vf+170 (342 in this case) and the added dynamic pressure nearly equals the loss of angle of attack, and we can maintain that rate up to the upper 20s, when it begins to taper dramatically. Approaching the mid-30s, we're closer to 300fpm. But at that weight, we'd be capped at around FL320 or 340 for a couple hours.

Cheers!

 

[erichartmann]

Spongbob,

Yeah, I'm sure. As AA points out, your cites are out of context and not relevant to the question.
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