Zoom Climb

[Thumpalumpacus]

I've always assumed that zoom was not just climbing, but climbing out of a dive to optimize the retention of speed gained in the dive.

 

[Ivan1GFP]

Zoom climb is not an angle. It is a sustained airspeed anywhere between best angle and best rate of climb. If you are faster than best rate and are climbing with a greater rate of climb than best sustained rate, you are at some point in a zoom climb. If you are at a sustained speed between those two points, you are at or between best rate and best angle.

You can be at best rate airspeed and accelerating if you are in a dive and you can be at best rate airspeed and decelerating if you are climbing. If in a dive, you are obviously not in a zoom climb. but, if your climb rate is better than normal best rate of climb and you are decelerating through best rate airspeed, you are in a zoom climb near the end of it because you won't have far to go before you stall or decrease your angle of climb so as to maintain airspeed.

This assumes, of course, that you are not in a jet fighter with a thrust-to-weight ratio better than 1. In that case, all bets are off since it doesn't follow normal climb procedures at high thrust values.

Hello GregP,
I can't say I agree with you. In a Zoom Climb, airspeed is not sustainable which is the point of why it is a zoom climb to begin with.
As I see it, you are flying a Zoom Climb any time you are exceeding the sustainable climb rate at the angle you have chosen and are trading speed for altitude.
I don't believe Best Rate and Best Angle are terribly relevant because both are at airspeeds much lower than we may be seeing.
Imagine you are trying to pull away from someone shooting at you. You are going 350 MPH while the other fellow is going 200 MPH, You want separation but you also want to gain some altitude as well. If you go too steep, you won't get the separation before you get shot. A high speed climb would not be a bad idea if you just pulled up by a couple degrees without bleeding off speed quickly. Would this be a Zoom Climb? I think so but it would be much shallower than angle at Vx or Vy.
Now imagine that you want to trade off speed for altitude so that you are slow enough to maneuver better. You choose to go into a near vertical climb. Is this a Zoom Climb? I believe so.

 

[GregP]

Hi Ivan1GFP,

You either didn't read my posts very well or I expressed poorly. Could be a bit of both, I can't say.

I agree with your first two sentences above.

Best rate and best angle ARE relevant because airspeed in a zoom climb decays, sometimes rapidly, depending on excess power. When it gets down near best rate of climb airspeed, it becomes VERY relevant.

If you ARE in zoom climb and stay there, at some point your airspeed will decay to best rate of climb airspeed. If you reduce your angle of climb so as to maintain that speed, you have transitioned to sustained rate of climb. If you don't, your rate of climb will continue to decay until you reach a sustainable airspeed or stall, whichver happens first.

Likely, we're saying much the same thing in different ways.

Cheers.

 

[Ivan1GFP]

Hello GregP,
I DID read your post and I believe the main disconnect is that you and I are discussing different objectives and how to achieve them.
From what I can tell, you are describing an aircraft with excess KE trying to convert that to altitude AND continue into a steady state climb at an optimal rate. I am interested in something quite different.

Take the very well known case of Robert Johnson in a Thunderbolt meeting up with a Spitfire Mk.IX.
Except for the initial performance comparison in a sustained climb, I don't believe Johnson was ever concerned about his climbing speeds at Best Rate Vy or Best Angle Vx.
He first used a bunch of high G load rolls to gain some horizontal separation and then a dive and high speed Zoom Climb to get enough altitude separation to safely turn without getting into Spitfire's shooting range in order to line up his own gunnery run.

The point is that in Johnson's Zoom Climb, he was never going to slow down to sustained climbing speeds so the Spitfire could catch up to him. That is the kind of game that I am thinking of.

It could have been a much more interesting match if the English pilot were another fellow named Johnson..... It wouldn't be nearly as easy to take that fellow for a ride.

 

[GregP]

Well, you are corre2ct about at least one thing ... we aren't talking about the same thing.

The title of the thread is Zoom Climb, not "a discussion of an encounter between Robert Johnson and a Spitfire IX."

I'd love to read a FACTUAL record of the event, but almost all I can find about it is unreferenced hearsay and "I heard it this way!"

I'll bow out and say that a P-47 should have a pretty good initial advantage over a Spitfire IC in a dive. Not too sure who would reach the ground first, but dive testing should answer that. According to WWIIaircraftperformacne.org, the P-47 was significantly ahead of the Spitfire in diving.

Also, according to them, zoom climb has never been satisfactorily settled by anyone when it comes to WWII fighters. I'd say I'm unlikely to manage that in few sentences.

 

[Greg Boeser]

Not too sure.

I was playing with you, not being obnoxious ... at least, I wasn't trying to be obnoxious.

If I can answer seriously, that's ballistic flight, but straight up? Don't know if that would be a zoom climb or not. I realize your question is basically a yes or no question, but ...

To me, a zoom climb is what happens when you are flying more or less straight and level, leave the power where it is or push it higher, and pull up into a climb that exceeds what your climb rate is once your speed decays down to best-climb speed. All the excess climb rate is zoom climb to whatever altitude you reach when the speed falls to best-climb speed. I never thought much of going vertical, but you go THROUGH vertical when you fly a loop in which, hopefully, you get to horizontal inverted at the top before running out of speed. If you don't, I suppose you just fall though the attempt. They showed a good one of those in ,"The Great Waldo Pepper."

So, the short answer is no, but heck, it might be. If we were in a Piper Cherokee 180, we might or might not get the nose vertical before we ran out of speed altogether. Might be fun to try it, might not be. Depends on whether or not you still have wings when you finish.

I remember watching a guy out in the country one summer day in a light plane doing exactly that, over and over. He would pull up til he was hanging on his prop, stall, recover and do it all again. This went on for a long time. I figure he (could have been a she) was practicing for an airshow.

 

[Ivan1GFP]

Well, you are corre2ct about at least one thing ... we aren't talking about the same thing.

The title of the thread is Zoom Climb, not "a discussion of an encounter between Robert Johnson and a Spitfire IX."

I'd love to read a FACTUAL record of the event, but almost all I can find about it is unreferenced hearsay and "I heard it this way!"

I'll bow out and say that a P-47 should have a pretty good initial advantage over a Spitfire IC in a dive. Not too sure who would reach the ground first, but dive testing should answer that. According to WWIIaircraftperformacne.org, the P-47 was significantly ahead of the Spitfire in diving.

Also, according to them, zoom climb has never been satisfactorily settled by anyone when it comes to WWII fighters. I'd say I'm unlikely to manage that in few sentences.

I only picked the Robert Johnson story to illustrate execution of a Zoom Climb that really had not much connection to Vx and Vy speeds or angles. We only have one witness to the story, Johnson himself, but the story is fairly credible when comparing performance between Spitfire IX and Thunderbolt. As noted before, this unknown Spitfire pilot was willing to fight to his own aircraft's disadvantages. A smarter pilot would not have done that.

As for comparison of Zoom Climbs, that was the original point of this thread and I don't know that we really have much more anecdotal evidence to do any comparisons except where the performance is extremely different.
I originally tried to propose characteristics that would affect Zoom Climb but at that point, we couldn't all agree as to what qualified as a Zoom Climb.

 

[GregP]

It's kind of like herding cats, huh?

Not simple to get any two to agree, much less 3 or more.

 

[gumbyk]

Also, according to them, zoom climb has never been satisfactorily settled by anyone when it comes to WWII fighters. I'd say I'm unlikely to manage that in few sentences.

I guess because 'zoom' climb hasn't been adequately defined.

 

[GregP]

Should be easy. My try might be: It is any climb rate higher than a sustainable climb rate.

If you are climbing better than you really can, you are in the process of trading kinetic energy for potential energy ... or speed for height.

If you stop trading energy by slowing the rate of climb so you are at a sustainable rate, you are no longer in a zoom climb.

 

[gumbyk]

Should be easy. My try might be: It is any climb rate higher than a sustainable climb rate.

If you are climbing better than you really can, you are in the process of trading kinetic energy for potential energy ... or speed for height.

If you stop trading energy by slowing the rate of climb so you are at a sustainable rate, you are no longer in a zoom climb.

At what power setting?
Are you able to change power to max climb, or is it combat power, or cruise?

 

[SaparotRob]

Anyone else reminded of an episode of The Big Bang Theory?
"There is a solution but it requires spherical airplanes in a vacuum".

 

[GregP]

At what power setting?
Are you able to change power to max climb, or is it combat power, or cruise?

Doesn't matter what power setting; at max power, there is some sustainable climb rate.

Any climb rate more than the max sustainable climb rate is a zoom climb. But, zoom climb CAN be less than max sustainable climb rate if you are at reduced power.

Nevertheless, any climb rate in excess of sustainable climb rate at max power IS a zoon climb. There are other definitions for zoom climb below max power that involve being above sustainable climb rate at the currently-set power level.

So, basically, if you are at a climb rate above the sustainable climb rate for your current power level, you are in a zoom climb, likely with speed decaying toward somewhere between best rate airspeed and best angle airspeed.

 

[GregP]

Big Bang was a good series for comedy with occasional decent humor about physics and math.

My favorite character is Penny ... but all were decent actors in their parts.

I also used to like, "Are You Being Served?", at least in its time period. Might still be funny; might not ... unsure.