Which is faster?

[GVFlyer]

Thanks for your concern, BBB.

The jury is still out.

I used to run the Aviation Managers and Pilots Seminar at Gulfstream Workshop. When we first started making airplanes that could spend several hours at 51,000 feet, we also were concerned about the risks associated with high altitude flight. I found the foremost expert in the field, Dr. John Wilson, FAA Atmospheric Ionizing Radiation chief scientist, and had him present his findings at the seminar.

Fundamentally, he stated that the predictions of those forecasting radiation pathology associated with high altitude flight were anecdotal and theoretical in nature. His direct observations based on NASA probes showed no verifiable correlation between high altitude flight and pathology and he further stated numerous surface based activities that presented similar exposure to radiation.

GV

 

[Daytonaflyer]

Alex,
If you are asking about a controlled experiment, with no wind, no aircraft performance differences, and no atmospheric variations, the results would be equal. It will not make a difference if you climb fast or slow.
There is a similar, but opposite situation in aviation called being "On the Step". It involves a descent rather than a climb. There is a theory that if you descend rapidly, you will travel farther in less time than you would if you were to descend slowly. This is a myth.
If you were to begin a rapid descent and then level off, your groundspeed would increase initially, but then rapidly decrease after you level off. Ultimately your airplane would travel exactly the same distance across the ground as it would if you were to descend slowly and then level off at the same altitude.
Also the groundspeeds in both situations should become equal shortly after level off. This theory applies to climbs too...of course we fly in the real world, not in a laboratory, and wind, aircraft performance, and atmospheric variations always are a factor.

 

[Big Beer Belly]

Fundamentally, he stated that the predictions of those forecasting radiation pathology associated with high altitude flight were anecdotal and theoretical in nature. His direct observations based on NASA probes showed no verifiable correlation between high altitude flight and pathology ...
GV

Thanks GV ... there's no argument we're being exposed to the increased radiation ... just whether someone can correlate pathology with it. My interest in this subject is genuine, as it affects me also.

BBB

 

[NJAFracPilot]

Alex,
If you are asking about a controlled experiment, with no wind, no aircraft performance differences, and no atmospheric variations, the results would be equal. It will not make a difference if you climb fast or slow.

And this is relevant to flying on this planet how?

If you were to begin a rapid descent and then level off, your groundspeed would increase initially, but then rapidly decrease after you level off. Ultimately your airplane would travel exactly the same distance across the ground as it would if you were to descend slowly and then level off at the same altitude. Also the groundspeeds in both situations should become equal shortly after level off.

What if you were flying in GVFlyer's G550 where his top speed is at 32,000 feet? He can do 510 knots at 32,000 feet or 340 knots at 1,000 ft. How much more ground is he going to cover if he hustles down to low altitude where he's 170 knots slower?







.

 

[GVFlyer]

Thanks GV ... there's no argument we're being exposed to the increased radiation ... just whether someone can correlate pathology with it. My interest in this subject is genuine, as it affects me also.

BBB

One additional data point on high altitude radiation effects on pilots - you are much safer behind glass with it's much lower transmission rates than you are behind acrylic or plastic.

In other words, you need to be behind a PPG windshield as they are the only company right now who knows how to bend glass.

GV

 

[AC560]

Thanks GV ... there's no argument we're being exposed to the increased radiation ... just whether someone can correlate pathology with it. My interest in this subject is genuine, as it affects me also.

There doesn't seem to be any medical issues with any of the Concorde pilots and some of those guys logged a lot of hours FL500+.

 

[time builder]

Using climb power in the BE99, you usually get better than cruise speed in a 500 ft/min climb with climb power until you're travel limited at say 15000. I'm sure most turboprops behave similarly.
My main considerations are departure proceedure (direction and climb requirements), and winds aloft.
Don't be like the guy I know who got busted for climbing at 500 fpm with a steeper climb gradient required, even though he was in VMC.

 

[Sig]

The Metro would almost always show the same rate of climb at 140 and 180 KIAS.

Not to sully a dang fine thread (thanks for the fantastic post, GV), but I have myself an idear:

This was demonstrated to me in a King Air 200 by a 757 AA CA. He spoke for literally ten minutes straight, saying this is a perfect piece of information which, when used, separates the pilots from the aviators.

He kept calling it L/D Max, L/D Max... I understand the drag curve and performance, and where you can get the dreaded bimodal distribution (you get the same climb at two speeds), but there is no free lunch in physics. Those two humps will come together at some regime.

My question (BBB or GV or any other Carl Sagan Gene. E. Yuss) is this: What is the key to causing this? It happens on a 757, it happens on a Metro, it happens on my Dash 8, it happens on BE20s.

L/D Max with TWO humps (local maxima, makes sense, just a bit o' caculus... ) but what be the variables that are germane to just this behavior?

FWIW: You can get THREE speeds with exact rates on the Dash8 100- it depends on how much you rely on deck angle for climb versus airspeed and how dense the atmosphere is (125kt, 160, and 192/3Kt get you 1000' fpm until about 5000 feet, and the high number decays to maintain the rate until meeting at 160 around 10-12). But wait- I thought we clumbed up there because of excess thrust? Is it parasite drag curve over an induced drag curve ALL under the excess thrust available, with the vector of thrust boogering up the numbers and creating the very low number, or do the forces involved just magically mesh?? Or do I need to have a glass of STFU and play pilot in my little trash 8 and forget about it?

**Gee, the answer is right in front of me. Buck-60 is the profile for climb, usually getting 1000 or so... The magic number seems to be +/- 35 knots or so and that's where the neat stuff happens. Makes a HUGE difference if you're flying the wrong way on the initial departure (SLOOWWW GS), or if you're in a hustle doing a parabolic to get home early.

 

[Coool Hand Luke]

Thanks GV ... there's no argument we're being exposed to the increased radiation ... just whether someone can correlate pathology with it. My interest in this subject is genuine, as it affects me also.

BBB

With that beer belly I think radiation exposure at high-level cruise is the least of your worries. (how do you get/keep a medical with that anyway?)

 

[MalteseX]

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.

Disregarding winds (or assuming winds are 0) and fuel consumption (you have all the money you need , or hedged your fuel in 1999--or Uncle Sam is paying for gas and you have BIG tanks (KC-10));
Flying at "barber pole" speed throughout the climb. Level off at 27500 to 29000 (depending on temp from STD) and cruise there --where a turbofan will get the greatest TAS at barber pole. Climb at best rate .......