The Zero's Maneuverability

[Geoffrey Sinclair]

wrathofatlantis = Gaston, who has spent many years promoting the basic idea WWII fighters the history books say were best horizontal were actually best vertical and vice versa, from a message of mine over three years old

A calculation Flak vs. B-17

www.britmodeller.com

All the following flowing from the search string, " "Society of Experimental Test Pilots" P-51 F4U P-47 "

Part of their report is quoted at F6F, FG-1, P-51, P-47 comparison Things like they kept to 6G or less given how irreplaceable the aircraft are.

Now would it be correct to say hello Gaston? And these ideas have been put forward for the last 10 or more years which sort of means why haven't the claimed tests been done by now? See for example, Spitfire IX v. FW 190A A thread which does far more than I could pointing out the flaws in the turning fighter ideas, let alone the use of the data. In one of the posts, is,

"For more of Gaston's theories visit the Aces High board and the UBI Il-2 General Discussion forum."

Johnny Johnson, maths and the 1989 Society of Test Pilot report; revisited.
N1K1, Ki-100, Ki-84, and why math is not predictive... - Topic Powered by Social Strata
FW-190A-8 turn superiority over FW-190D-9 confirmed - Topic Powered by Social Strata"

Another visitation is at http://forum.1cpublishing.eu/archive/index.php/t-15392.html

I note the similarities of the turning fighter advocay across the years, and here for example,

I note the posting of "never catching fire" was done without qualification, then the walk back as someone else's words.

I note back then whether true or indicated air speeds were being quoted, and not answered.

Asked for Shaw, twice, no reply

Asked where the high speed came from given Eric Brown's description did not have the phrase, no reply

Darwin Spitfires page, no reply.

How were the Spitfire escorts versus FW190 interceptor combats missed? No reply.

Closterman is a reference for turning Fw190, his reports of diving ones ignored.

The failure to provide the where a quote from "First Team" was located while ignoring the Appendix 5 information.

The way Hartman kept being hit by debris as proof diving tactics had problems.

The failure to explain whether the Ki-61 was a turn fighter, given the Ki-100 was claimed to be one.

The Spitfire combat fuel consumption figure, ignored.

The flipping where test pilots are wrong or right depending on what their data is.

The misreading of text as a method of changing the subject.

I noted Lerche making the report about La-5 versus Fw190 and Bf109. The reply was another absolute, *only* German source, so someone has read/interviewed all the relevant personnel and reports. No thought of for example, as the reports tend to use 8-109 and 8-190 that there might be a transcription error, or the way the Bf109G stalled about 20 mph slower that the Fw190A and with much better stall warning, so maybe the Fw190 was not going to push things at low altitude where a stall would be fatal, instead it is an absolute, truth laid down, and later Lerche, having provided contradictory information is attacked as a "usual suspect".

Essentially information that does not fit is ignored or alternatively the person (or aerodynamic theory) who presents it is attacked. All far from the front lines applies even more to all of us today. The past is most definitely gone and someone has a very fixed idea about it.

 

[wrathofatlantis]

Quote: "Cool. Let's hear those anecdotes."

You might start with:

• Spitfire Pilot: An Extraordinary True Story of Combat in the Battle of Britain, Roger Hall - Amazon
• Spitfire – A Very British Love Story – Jihn Nichol
• Spitfire – Flying the Icon – Jarrod Cotter
• Spitfire Pilot, Davis Cook

Oh wait, I know, try Google! Search for "books about the Supermarine Spitfire." You'll probably find a bunch of books on the Spitfire, too, like I did. I own about 6 - 8 of them.

You are the only person in the last 60 years I ever heard say the Zero and Spitfire can't dogfight. Wing loading alone would make me curious. I'm curious how is it possible you can find obscure quotes to bring forth your contentions above and yet miss the rest of the folklore depicting these two iconic aircraft as premier fighters of their time, especially in the dogfight area. Let's just say there is a lot of opinion out there that runs runs contrary to your contentions and let it go at that.

The guys I know who fly Spitfires today have a universal high regards for it's power-to-weight ratio and it's maneuverability. The Griffon units are very nose-heavy on the ground and take care with ground operations to not nose over with brakes.

There are any number of threads in here about the Spitfire.

Cheers.

I have read or at least perused hundreds of Spitfire books... None held the specific fw-190A examples that you claim.

I also explained that at high altitude, or high speeds, the Spitfire does out-turn the fw-190A. I also explained that below one circle it can point its nose inward in a stall, giving the "illusion" of out-turning.

At least three books I read mentioned the slow (and especially heavy) Spitfire roll rate from the Mk IX onward. But, as I said, the roll rate was not that important in combat. It is just an example of the general incapacity at detecting anything specific by the general consensus (maybe because of the good roll of the Mk V?).

I did not say the Zero airframe could not circle fight well. I said that its pilots did not do so by doctrine, and this was criticised by US Navy pilots: Quote from Justin Pyke:

1:01:42 USN pilot comment (27 September 1942): "In my opinion, they [Zero pilots] had generally poor fighter tactics: Zeros could not be shaken by us if they would chop their throttles and sit on our tails (meaning chopping the throttle and turn)."

So you are blatantly misrepresenting my position.

I asked for a specific example of a Spitfire out-turning a fw-190A during multiple horizontal circles.

Yes I do ask for specific examples and not general statements, while I consider general statements stronger for my case.

The reasoning is simple: The overall uninformed consensus is wrong (Eric Brown zero single engine kills etc), therefore more examples of general statements do not strengthen the case, since these statements could simply ape the overall uninformed consensus.

On the other hand, general statements that go counter to the overall consensus, and from people with actual first hand knowledge (Clostermann and Johnson 30+ fw-190 kills), are obviously stronger given the absence of a general consensus to support them.

These statements should not exist at all, especially from such sources.

That is why I ask for specific examples. And until you do I will leave it at that.

 

[wrathofatlantis]

wrathofatlantis = Gaston, who has spent many years promoting the basic idea WWII fighters the history books say were best horizontal were actually best vertical and vice versa, from a message of mine over three years old

A calculation Flak vs. B-17

www.britmodeller.com

All the following flowing from the search string, " "Society of Experimental Test Pilots" P-51 F4U P-47 "

Part of their report is quoted at F6F, FG-1, P-51, P-47 comparison Things like they kept to 6G or less given how irreplaceable the aircraft are.

Now would it be correct to say hello Gaston? And these ideas have been put forward for the last 10 or more years which sort of means why haven't the claimed tests been done by now? See for example, Spitfire IX v. FW 190A A thread which does far more than I could pointing out the flaws in the turning fighter ideas, let alone the use of the data. In one of the posts, is,

"For more of Gaston's theories visit the Aces High board and the UBI Il-2 General Discussion forum."

Johnny Johnson, maths and the 1989 Society of Test Pilot report; revisited.
N1K1, Ki-100, Ki-84, and why math is not predictive... - Topic Powered by Social Strata
FW-190A-8 turn superiority over FW-190D-9 confirmed - Topic Powered by Social Strata"

Another visitation is at http://forum.1cpublishing.eu/archive/index.php/t-15392.html

I note the similarities of the turning fighter advocay across the years, and here for example,

I note the posting of "never catching fire" was done without qualification, then the walk back as someone else's words.

I note back then whether true or indicated air speeds were being quoted, and not answered.

Asked for Shaw, twice, no reply

Asked where the high speed came from given Eric Brown's description did not have the phrase, no reply

Darwin Spitfires page, no reply.

How were the Spitfire escorts versus FW190 interceptor combats missed? No reply.

Closterman is a reference for turning Fw190, his reports of diving ones ignored.

The failure to provide the where a quote from "First Team" was located while ignoring the Appendix 5 information.

The way Hartman kept being hit by debris as proof diving tactics had problems.

The failure to explain whether the Ki-61 was a turn fighter, given the Ki-100 was claimed to be one.

The Spitfire combat fuel consumption figure, ignored.

The flipping where test pilots are wrong or right depending on what their data is.

The misreading of text as a method of changing the subject.

I noted Lerche making the report about La-5 versus Fw190 and Bf109. The reply was another absolute, *only* German source, so someone has read/interviewed all the relevant personnel and reports. No thought of for example, as the reports tend to use 8-109 and 8-190 that there might be a transcription error, or the way the Bf109G stalled about 20 mph slower that the Fw190A and with much better stall warning, so maybe the Fw190 was not going to push things at low altitude where a stall would be fatal, instead it is an absolute, truth laid down, and later Lerche, having provided contradictory information is attacked as a "usual suspect".

Essentially information that does not fit is ignored or alternatively the person (or aerodynamic theory) who presents it is attacked. All far from the front lines applies even more to all of us today. The past is most definitely gone and someone has a very fixed idea about it.

No specific combat examples of Spitfires out-turning fw-190As in consecutive circles below 20 000 ft..

Hans-Werner Lerche was the Luftwaffe's Eric Brown, a test pilot who came to similar misguided conclusions. His descriptions show the typical test pilot bias towards high speed high G un-sustained turns (explaining how the 109G magically out-turns the 190A).

Again, it is always test pilots far from the frontlines that support your points. Isn't that a noteworthy trend?

 

[GrauGeist]

Again, what the hell is "circle fighting"?

Is it a horizontal turning fight or does it cover all aspects of a typical dogfight?

If not, is there also "loop fighting", "corkscrew fighting" and more that I'm not aware of?

 

[MiTasol]

obviously circle turning is some cheap flight sim jargon.

 

[GregP]

I have read or at least perused hundreds of Spitfire books... None held the specific fw-190A examples that you claim.

I also explained that at high altitude, or high speeds, the Spitfire does out-turn the fw-190A. I also explained that below one circle it can point its nose inward in a stall, giving the "illusion" of out-turning.

At least three books I read mentioned the slow (and especially heavy) Spitfire roll rate from the Mk IX onward. But, as I said, the roll rate was not that important in combat. It is just an example of the general incapacity at detecting anything specific by the general consensus (maybe because of the good roll of the Mk V?).

I did not say the Zero airframe could not circle fight well. I said that its pilots did not do so by doctrine, and this was criticised by US Navy pilots: Quote from Justin Pyke:

1:01:42 USN pilot comment (27 September 1942): "In my opinion, they [Zero pilots] had generally poor fighter tactics: Zeros could not be shaken by us if they would chop their throttles and sit on our tails (meaning chopping the throttle and turn)."

So you are blatantly misrepresenting my position.

I asked for a specific example of a Spitfire out-turning a fw-190A during multiple horizontal circles.

Yes I do ask for specific examples and not general statements, while I consider general statements stronger for my case.

The reasoning is simple: The overall uninformed consensus is wrong (Eric Brown zero single engine kills etc), therefore more examples of general statements do not strengthen the case, since these statements could simply ape the overall uninformed consensus.

On the other hand, general statements that go counter to the overall consensus, and from people with actual first hand knowledge (Clostermann and Johnson 30+ fw-190 kills), are obviously stronger given the absence of a general consensus to support them.

These statements should not exist at all, especially from such sources.

That is why I ask for specific examples. And until you do I will leave it at that.

I like this forum, but I am not going to research your opinion for you. Work on it yourself. The Spitfire books I have described it's maneuverability quite well.

No combat pilot gets an "illusion" that he turns better than opposition if it isn't true. They stick around for the entire fight, not just for one turn. If he can't out-turn the enemy, he will try something else and won't claim he can.

You've done a good job stating your position. I don't have to expound on it and won't. As I said above, we'll just have to agree to disagree .... unless you really are Gaston, in which case I decline to argue with you as it has been shown to be a waste of time. sic transit glorioski or fame is fleeting.

If you aren't Gaston, that does not apply, and your mileage may vary.

There are comparative turn times available for many fighters. The Zero and the Spitfire are among the best of all of them. Makes you wonder why the pilots of those two airplanes would not use the strengths of their mounts in a fight, huh? If I were flying a Spitfire in combat, and I'm not ... I'd try to use it as best I could. That might very well include dogfighting. In a Zero, hard turning is your best tactic since you aren't going to out-run a late-war Allied fighter.

Cheers.

 

[SaparotRob]

There's Kung Fu fighting.

 

[GregP]

Those guys are fast as lightning ... and it takes expert timing!

 

[Greg Boeser]

I like this forum, but I am not going to research your opinion for you. Work on it yourself. The Spitfire books I have described it's maneuverability quite well.

No combat pilot gets an "illusion" that he turns better than opposition if it isn't true. They stick around for the entire fight, not just for one turn. If he can't out-turn the enemy, he will try something else and won't claim he can.

You've done a good job stating your position. I don't have to expound on it and won't. As I said above, we'll just have to agree to disagree .... unless you really are Gaston, in which case I decline to argue with your as it has been shown to be a waste of time. sic transit glorioski or fame is fleeting.

If you aren't Gaston, that does not apply, and your mileage may vary.

There are comparative turn times available for many fighters. The Zero and the Spitfire are among the best of all of them. Makes you wonder why the pilots of those two airplanes would not use the strengths of their mounts in a fight, huh? If I were flying a Spitfire in combat, and I'm not ... I'd try to use it as best I could. That might very well include dogfighting. In a Zero, hard turning is your best tactic since you aren't going to out-run a late-war Allied fighter.

Cheers.

The Zero, when introduced, was fighting biplanes and first gen monoplanes in China. It was the energy fighter in that conflict. So it makes sense that the tactics developed stressed high speed passes and avoiding turning fights. Then, when the combat environment changed, they were slow to adapt.

 

[GregP]

The Zero, when introduced, was fighting biplanes and first gen monoplanes in China. It was the energy fighter in that conflict. So it makes sense that the tactics developed stressed high speed passes and avoiding turning fights. Then, when the combat environment changed, they were slow to adapt.

Not according to pilots who were there. I've heard maybe 100 of them speak about it and everyone who fought with a Zero said it was suicide to try to turn with a Zero, so they followed their training and didn't. If the victim doesn't start a turning fight when he is attacked, the attacker won't BE in a turning fight.

It was the same on the Russian Front when the Bf 109 was better than the La-5 and Yak-9 at higher altitudes. The Soviets declined to GO to higher altitudes and instead attacked the ground troops. The Germans were left with the decision of whether to stay high and watch their troops get killed or come down and fight. They elected to come down and fight, which was right in the best envelope for the Soviet fighters.

As for the Zeros, if they could GET the Allied airplanes to dogfight, they were happy. If they couldn't, they fought as best they could.

War in fighter aircraft has never been about you making a plan and then somehow forcing your opponent to follow your plan.

 

[GrauGeist]

Once the P-40 pilots caught on to the A6M's turning ability in a lower- speed dogfight, they used the P-40's superior turning ability at higher speeds against it.

This holds true with the RAF's surprise when the Fw190 was introduced. It was soon found that the Typhoon was a match for the Fw190 at low to medium altitudes in a turning fight but that all changed when the British captured a JG52 Fw190 and evaluated it. The Spitfire Mk.IX was the result.

BTW, wasn't there an episode of Star Trek where Kirk and Spock had to circle fight?

 

[Thumpalumpacus]

My impression, from readings only, is that in China the Zero was very much BnZ as the planes it fought weren't very climby. And Lundstrom as well writes about slashing attacks upon Wildcats when Zeros used their climbing ability against Wildcats flying lower. Perhaps R Leonard can provide more info?

But against the Chinese fighters in 1940, the Zero had options. Chennault figured out that diving attacks provided safe ingress and egress against a plane his P-40s couldn't really turn with in a hairball. Before that, the Zero was used in BnZ.

 

[Greg Boeser]

Joe Bauer was one Wildcat pilot who was not afraid to turn with a Zero.

 

[GrauGeist]

The majority of "Zeros" encountered in China, were the KI-43, which was just as deadly.

The A6M was used briefly in the Chinese theater, but the majority of that front was operated by the IJA air elements.

 

[Holtzauge]

I like this forum, but I am not going to research your opinion for you. Work on it yourself. The Spitfire books I have described it's maneuverability quite well.

No combat pilot gets an "illusion" that he turns better than opposition if it isn't true. They stick around for the entire fight, not just for one turn. If he can't out-turn the enemy, he will try something else and won't claim he can.

You've done a good job stating your position. I don't have to expound on it and won't. As I said above, we'll just have to agree to disagree .... unless you really are Gaston, in which case I decline to argue with you as it has been shown to be a waste of time. sic transit glorioski or fame is fleeting.

If you aren't Gaston, that does not apply, and your mileage may vary.

There are comparative turn times available for many fighters. The Zero and the Spitfire are among the best of all of them. Makes you wonder why the pilots of those two airplanes would not use the strengths of their mounts in a fight, huh? If I were flying a Spitfire in combat, and I'm not ... I'd try to use it as best I could. That might very well include dogfighting. In a Zero, hard turning is your best tactic since you aren't going to out-run a late-war Allied fighter.

Cheers.

Yes, and just by looking at basic data like wing- and span loading for the Fw-190 and the Spitfire, this tells us that the latter will readily out-turn the former. It's not even close.

Speaking of quotes, I remember RAF Spitfire MkV pilots complaining that "turning does not win battles" when their top brass tried to smooth things over when they were getting beat up by the Fw-190A in 1941. Because this was all that the Spitfire pilots had in the tool box at the time: Their turning superiority, and they were getting frustrated that the Jerries did not play ball and only engaged in slashing attacks, refusing to turn with them (for obvious reasons!).

And this of course explains why there are no anecdotes of "Spitfire out-turning fw-190A during multiple horizontal circles": Not because the Fw-190 out-turned the Spitfire, but simply because most Germans were sensible enough not to turn with a Spitfire, and those that did were shot down in short order long before they had completed anything like "multiple horizontal circles".

At first I thought maybe wrathofatlantis was engaging in some really high level trolling, but it really seems like he is serious about all this. So I think the best course of action is :


View: https://giphy.com/gifs/the-simpsons-scared-homer-simpson-jUwpNzg9IcyrK

 

[Engineman]

Looking at the material posted about the "Zero", I think the best info is the "Informational Intelligence Summary No 85" which says don't go below 300mph Indicated airspeed!
Also, it emphasises the slow roll rate of the Zero at high speeds and the fact that the engine cuts under negative -G.
The Aussie tech docs are also great.

Eng

 

[Holtzauge]

Looking at the material posted about the "Zero", I think the best info is the "Informational Intelligence Summary No 85" which says don't go below 300mph Indicated airspeed!
Also, it emphasises the slow roll rate of the Zero at high speeds and the fact that the engine cuts under negative -G.
The Aussie tech docs are also great.

Eng

Yes, that is a good document and an interesting summary. And the top speed for the Sakae 12 engined variant in that report is the highest I've seen: 326 mph. Granted, those speeds in that document were not corrected for compressibility, but even knocking off a mph or two for that, still quite fast. But IIRC then they did the test at 2600 rpm's, which is a bit higher than the 2500-2550 I've seen from Japanese data. But the top speed of the A6M2 variant with the Sakae 12 engine seems to be an area of contention: there are many different numbers out there to choose from.

 

[Engineman]

A good point (I summarise it) is made in summary No 85 on page 3, para 2, item 3, Never follow a Zero into a climb at low speeds, as you slow and stall (or have to reduce climb rate), the Zero can complete a "loop" to position for a rear quarter attack.
So this "loop" would probably be a continued and tightened pull up and back in a normal looping manoeuvre, back onto the tail of the (previous) pursuer wallowing below. This is quite a thing, and remember the Zero was being flown by a test pilot with relatively little experience of the type.

Eng

 

[Geoffrey Sinclair]

No specific combat examples of Spitfires out-turning fw-190As in consecutive circles below 20 000 ft..

No specific reply to any of my questions.

Hans-Werner Lerche was the Luftwaffe's Eric Brown, a test pilot who came to similar misguided conclusions. His descriptions show the typical test pilot bias towards high speed high G un-sustained turns (explaining how the 109G magically out-turns the 190A). Again, it is always test pilots far from the frontlines that support your points. Isn't that a noteworthy trend?

The noteworthy trend is the use of selected quotes, Hans-Werner Lerche is liked when a quote fits the conclusion, disliked if not. Sort of like one person who found a selection of quotes to prove the USAAF would have won the air war over Europe earlier if not hampered by the ineffective RAF but the RAF was the only force that could have completed the stopping of German oil production thereby ending the war by late 1944.

The Big Show, Pierre Clostermann, years since I have read it, flying a Tempest and noting the Spitfire IX did not have the performance to force combat with the latest Luftwaffe fighters. He writes the Germans respected the Spitfire dog fighting ability and in the encounter he describes the Germans were fighting in the vertical. I can no longer recall if the opponents were Fw190D or Ta152 and whether the word usual was used to describe the German tactics but I am sure someone has access to the book and can find the passage.

Consider the 1940 or so requirements for a naval fighter. One bomb on a ship can cause a lot of damage, interception time limited, probably only one chance at a vertical pass which is unlikely to break up the attack, horizontal fighting ability means you stay with the incoming strike aircraft while being able to defend against escorts, helps explain the Zero the FM-2 and F6F turning abilities, especially at bomber cruise speeds but the overlap between turning ability and short take off and landing ability also contributes. Then again when rated the F4U had the worst turning circle of the US fighters.

 

[wrathofatlantis]

obviously circle turning is some cheap flight sim jargon.

I explained in this very thread where I took it from:

"On October 21, 1943, the Group launched eight aircraft along with four Mustangs from the 530th on a big Japanese supply dump at Kamaing in Burma. The 530th squadron's P-51As met numerous Mitsubishi Zeros when they accompanied B-24s and B-25s on bombing missions. On the way down, I came up behind Lt. Geoffrey Neal, who was chasing a Zero [Mitsubishi A6M] down to the deck! I latched on to their formation and watched as he drove the enemy fighter right into the ground. The pilot of the Zero had tried everything to get rid of Lt. Neal except to circle fight. At this point, Lt. Arasmith had two confirmed kills, but the fight wasn't over…"-311th Fighter Group Unit history


Circle fighting is simply consecutive same side horizontal or near-horizontal 360 degree turns.

It is more clear than dogfighting, because dogfighting is a general term that could include successive vertical loops or turn reversals. Vertical loops would not look like a stable circle.

If you want a clue how extensive circle fighting was in WWII, I have found for 1944 four examples of P-51 vs Me-109 circle fights near the deck where the consecutive turns went on for 30 straight minutes in 3 cases, and 15 minutes in one case. There is another one of 10 minutes, so 30 consecutive 360s narrated by Clayton Kelly Gross.

And yes, they had to be consecutive with no side switching if you understand the roll reversal rule once committed into the circle.

At an average of roughly 20 seconds per 360, this means 3 1944 examples of 90 consecutive 360 degree circles, plus one of just 45 consecutive 360 circles.

And people have to ask what circle fighting is... Because all they have seen is video games.

Given the above, it seems to be surprisingly hard to find a single example of a Spitfire going past 1 circle or 2 circles, below 20 000 ft. and gaining on a FW-190A, especially for a 50% wingloading advantage...

As for those who think the Spitfire example is a physical impossibility, it is just as possible as an engineless car pushed only by the wind being 2.8 times faster than the wind pushing it.

If you understand the difference between Force and Energy, you understand that the shape of objects, by their complexities, allows you to get more Force, and thus more Potential Energy, out than you put in: A physics professor failed so completely to understand this, still thinking Energy output is limited to below a one to one ratio, that he bet $10 000 it was not possible for the engineless car to be faster than the wind pushing it.

He of course lost.:


View: https://youtu.be/yCsgoLc_fzI?si=bRUGVjIzd-uqp4dX

The explanation offered with the trolley example (at 13:29) is relatively poor, however, because the trolley description ignores the issue of ratio. He only speaks of the differential of speed between two mediums.

Instead, look at the trolley/wood beam example, and make the bottom wheels infinitely small, so that they will rotate 3000000000000000000000000000000 times for a micron of movement: Because this is transferred to a larger diameter axle contacting the big wheel, if you make the 4 bottom wheels small enough (on a raised toothed rail), and make them turn without slipping (toothed on toothed rails, and toothed big wheel all around), a mere contact push with your finger, barely depressing the skin of your finger, would (theoretically) send the trolley out to near the speed of light, into outer space.

Making the wheels that small and still strong enough to have them function is of course impossible, but the basic principle is simple enough: The trolley simply demultiplies distance with a ratio: 1 mm from your finger could be converted (instantly) into 300 000 kilometers, if the bottom 4 wheels were small enough.

The problem is, the distance "conversion" of the trolley is instantaneous, which would break the teeth or otherwise cause slippage with too massive a wheel ratio.

In the case of the FW-190A, what is instantly "converted/multiplied" is the compression of air between the prop and the wing, creating lift from the longitudinal tension between prop and wing, from an unknown ratio effect.

Reducing the prop power increases the ingestion of air between the wing and prop, increasing the compression, which is why your hear of not only the throttle being reduced, but of it staying reduced during multiple 360s.

And that is why the FW-190A out-turning the Spitfire is absolutely possible. It's called a ratio.

I will now wait for that one Spitfire gaining below 20 000 ft example.