Which is faster?

[Alex Chilton]

Just wondering, given a constant power setting, say at an N1 of MCT, is it faster to climb to your flight level asap or to fly as fast as possible during the climb while maintaining a 500 fpm climb?

Does anyone have any data to support either argument? It seems like pilots that are behind schedule like to decrease the rate of climb and increase the airspeed on the way up. My hunch is that it would be faster to climb on up to cruise where the engines are more efficient and your TAS is higher.

 

[mar]

All things being equal, it depends...

...on the winds aloft.

I'd say if you're gonna be bucking some pretty stiff headwinds, you're better off with a high speed climb to minimize your exposure to the headwinds.

But if ya got some rippin' tailwinds, then you might as well climb right on up and enjoy the ride.

Anyway, that's what I used to do when I was flying turboprops and I was late.

 

[Lead Sled]

Just wondering, given a constant power setting, say at an N1 of MCT, is it faster to climb to your flight level asap or to fly as fast as possible during the climb while maintaining a 500 fpm climb?

Does anyone have any data to support either argument? It seems like pilots that are behind schedule like to decrease the rate of climb and increase the airspeed on the way up. My hunch is that it would be faster to climb on up to cruise where the engines are more efficient and your TAS is higher.

It depends upon so many things. One thing is for sure, your specific range will probably suffer anytime you climb "off schedule" and any time savings you might achieve will be minimal at best. It's hard to make up time enroute. The time difference, coast-to-coast, between M.76 and M.80 is what 15 minutes? But it sure makes the passengers feel good if they think you're trying to make up the time.

'Sled

 

[Big Beer Belly]

Just wondering, given a constant power setting, say at an N1 of MCT, is it faster to climb to your flight level asap or to fly as fast as possible during the climb while maintaining a 500 fpm climb?

Does anyone have any data to support either argument? It seems like pilots that are behind schedule like to decrease the rate of climb and increase the airspeed on the way up. My hunch is that it would be faster to climb on up to cruise where the engines are more efficient and your TAS is higher.

Many of UPS's flights into the next day air sorts are "time critical" and operate on "minimum time enroute" flight plans. Plugging the "go fast" cost index into the FMC ALWAYS produces an acceleration to "barber pole" as soon as legal and maintains it throughout the climb, cruise and descent. The flight planning software is quite sophisticated (supposedly!) accounting for winds, aircraft weight, various routings and altitudes, etc... yet ALWAYS has the aircraft accelerate to maximum allowed speed as soon as possible.

Therefore, I'd say sacrifice climb rate for speed (while maintaining 500 fpm min) in order to reduce enroute time.

BBB

 

[jergar999]

Sometimes it may be somewhere in between as well. The Metro would almost always show the same rate of climb at 140 and 180 KIAS. Supposedly that had something to do with tail drag.

 

[GVFlyer]

Just wondering, given a constant power setting, say at an N1 of MCT, is it faster to climb to your flight level asap or to fly as fast as possible during the climb while maintaining a 500 fpm climb?

A lot depends on the winds aloft and the performance capabilities of your aircraft.

I don't file below FL450 unless I'm extremely heavy or the flight is an hour or less. I generally climb at 300 KIAS/KCAS until 300 knots intersects Mach 0.80 then M 0.80 thereafter.

My fastest cruise speed is the lowest altitude at which I can attain M 0.885, which is FL320 (actually 32,160 ft) because the higher the saturated air temp the higher the true airspeed, but it is grossly inefficient to fly at that altitude.

The winds generally drop off above FL390. So if I'm going East and there is a roaring wind out of the West, I may climb at 320kt/M0.83-85 thus flatening my climb somewhat through the twenties and thirties to take advantage of the wind.

Going West yesterday, I used M0.80 to FL470, to get there quickly and limit the time I was exposed to the headwinds. The G550 actually climbs faster with a low drag climb at M 0.80 than it will with a high drag climb at M 0.75. Reaching FL470 I still found I had 50 knots on the nose, so I cruise climbed at M0.84 and 500 fpm to FL490 where the headwind dropped to 22 knots.

If I was flying an aircraft that couldn't get out of the thirties, I'd climb at the fastest speed that would still give me a 500 fpm climb. Your manufacturer's cruise climb speeds are normally predicated on the most cost effective climb that will allow you to reach the maximum range capabilities of your aircraft, that is to say saving fuel, not time.


GV





~

 

[Alex Chilton]

BBB --

Thanks for the post. That is good stuff...I guess it pays to fly as fast as possible during the climb if you are behind schedule.

Alex C.

 

[Muddauber]

As usual GV, you hit the nail on the head. Good post.

Muddy

 

[GEXDriver]

GVFlyer -

Those are the same techniques I use in the Global, well almost. Not being an astronaut, I mostly use FL410 and FL430.

 

[Big Beer Belly]

Reaching FL470 I still found I had 50 knots on the nose, so I cruise climbed at M0.84 and 500 fpm to FL490 where the headwind dropped to 22 knots.

GV

~

YIKES GV! ... I'm sure you're well aware of the amount of radiation you are being subjected to at those altitudes <no grin> One our pilots (with a degree in nuclear physics I believe) once posted some alarming data at the dramatic increase in radiation as you climbed above 410. The polar routes have exposure limits due to the differences in ozone, etc..

Does your company provide such data? Are you limited in your flight hours due to exposure? Pregnant women are advised not to travel due to the greater risk of damage to a developing fetus at far lower altitudes. Just curious if you have any recent data. I've always been curious about this and what we're NOT being told.

BBB