Remember with ADS-B out, ATC can see your ‘selected’/‘wrong’ altitude so be careful doing this in a modern integrated cockpit…but yes, I do the same.
When you think about it, this isn’t about conservation of energy at all. It is about how to gain energy in the most efficient way. In this example in the video what is done is to accelerate from a set altitude at one speed and to a new speed at the same altitude (higher total energy by increasing speed exclusively). The aircraft flying at “the step” has flown a longer distance in 3D space, yet he catches up to the other and they fly at the same speed at the same alt from there on. Clearly the one that has flown a longer distance has done more work (in physical terms) and therefore is more efficient (both are flying at WOT all the time). It’s just that the extra work he has done is not very useful in getting from A to B when A and B are at the same altitude.
What the video shows is that gaining energy by climbing (at best L/D, or Vy I guess) is more efficient than gaining energy by accelerating from Vy in a straight line at a set altitude. So even if this adds up to nothing in the end, the persons in the video has got the physics all wrong.
You could say that going up and then down, cancels out the “work”, and this is true in general, but not here. The only work that is done here is to gain speed at a set altitude (accelerate the plane). The only forces working in this respect are thrust and drag. Work is distance * force. Both are running at WOT, equal force, but the one flying at the “step” has moved a longer distance in the air.
IMO, flying at the step is indeed a much more efficient way of flying, you travel a longer distance with the same power and the within the same time. But that added efficiency will not do you any good, because the added distance travelled is not the shortest distance from A to B.
You could say that all this video show is that the shortest distance from A to B is a straight line, and that the straight line principle is a good principle to follow when going from A to B, and B is a fixed point. But it has nothing to do with efficiency of flying.
Say for instance that when the “step” plane has reached it’s step altitude, they were told to turn 180 degree to a point C at the same alt as point B. The other plane wouldn’t have a chance. Also they could be directed to a higher altitude, the other aircraft would be equally left behind. Altitude is a more usable form of energy then speed in most circumstances, this is probably where this myth comes from? WWI or something?
LeSving, simplistically, both aircraft in the video are at the same altitude climbing alongside each other with WOT. Then one levels off and the other continues to climb, again with both at WOT, and they end up at the same altitude, same speed and same lateral distance…IOW they started and finished with equal energy states with the same energy input (E = P.t…where it is assumed they both produced the same amount of power throughout). Now some pedants may argue about power perhaps not being equal due to differing efficiencies at differing air speeds but for the range presented in the video I would say that effect is negligible….
By all means climb slightly high and dive to the required altitude….I do it as I said in my original post…but not for any gain in efficiency…just to reach a steady state sooner so I can adjust the mixture and relax…
In controlled airspace would the aircraft that climbed higher than the required level be quilty of a level bust? I am not an IFR pilot so just interested.
If you went over by 100ft, ATC would probably not complain. At 200ft they would because that if the transponder accuracy tolerance.
Am I wrong, thought it was 300ft.
ATC will start bitching if the displayed level on their radar is more than 200ft out. This error could be due to a (combination of a) number of factors such as accuracy of altitude keeping, accuracy of altitude encoder, pressure setting used etc. Please don’t think that you can bust your level by up to 200ft indicated on the altimeter and get away with things.
The original question – no. Just think it through for a minute or so.
If you want to get to your cruise speed faster, simply level off at your target altitude but stay on climb power until you’ve got the right AIS, no? What’s the point of climbing another 200ft then descending? The drag effect (less drag on the climb, more on the descent) will at best square off.
denopa wrote:
If you want to get to your cruise speed faster, simply level off at your target altitude but stay on climb power until you’ve got the right AIS, no? What’s the point of climbing another 200ft then descending? The drag effect (less drag on the climb, more on the descent) will at best square off.
The point was that you are so high that climb power has dropped to cruise power levels.
But we’re also talking about jets?
