Engine power vs altitude

If you're going to criticise someone, at least have the common courtesy to spell their name correctly.

Mike has put up hundreds (if not thousands) of original documents on WWII Aircraft Performance and made them freely available for all to look at and share. In doing so, he's performed a valuable service to almost all who use and enjoy this forum.

What have you done?

Yes Mike, thank you. No doubt he has provided us with original documents, a great service. He has also made glaring mistakes in HIS analysis of some documents, NOT the documents themselves.

altsym said:

Yes Mike, thank you. No doubt he has provided us with original documents, a great service. He has also made glaring mistakes in HIS analysis of some documents, NOT the documents themselves.

Click to expand...

OK, I'll bite. Where exactly does Mike insult der fuhrer's uber fighter?

Jabberwocky said:

If you're going to criticise someone, at least have the common courtesy to spell their name correctly.

Mike has put up hundreds (if not thousands) of original documents on WWII Aircraft Performance and made them freely available for all to look at and share. In doing so, he's performed a valuable service to almost all who use and enjoy this forum.

What have you done?

Click to expand...

I agree. You may or may not agree with his analysis, but his work in putting up data has been invaluable.
And that's the nice thing about it. You can make your own interpretations, it's all there for you to do it.

I often wonder why never been an "evaluation" of 109F and Spit 5 on ww2performance site. I guess Mike was not yet able to find bad enough graphs for 109Fs... Seriously, the bias of those articles are legendary in aviation community.. the errors (manipulations?) are well known.

The originals are good though. I prefer to read those and ignore these silly articles completely. I am sure everybody can find in originals what is interesting for him.

All Data from WWII Aircraft Performance, in their FW-190 section. Plus the Jumo 213A charts shown here.

I took various 801D numbers (all at max settings without C3).
Two sources agreed well. The USAAF tests, which I think were on a static rig to NACA specs. There are 2, with and without the geared fan.
These agree quite well with FW's own climbing numbers, that is without any (or minimal) RAM air.
The FW numbers are on level flight, that is with ram air increasing boost. This increases power and delays FTH.
I suspect the very high altitude ones (30,000ft+) are a bit high, because by that point IAS would be getting very low.

A very important factor often forgotten, especially with Merlins on high boost, they couldn't always get the 25lb boost without high speeds ramming air into the intakes.

Basically the BMW numbers look good, excepting the very high altitude with ram air, and overall cross check quite well.

Now the Jumo 213A numbers, taken from charts shown here with no MW-50 or GM1, but at 3,250 rpm, thus basic maximum power numbers without power boosting.
I assume they include ram air, but then again? Confirmation from anyone would be nice. If they are static then the correct comparison would be with the 801 static (or climbing) numbers.

Now I took the numbers at min/max values and back calculated the in between ones, to enable like by like comparisons.
PS is corrected for to BHP. KM to feet.
The X-axis is chosen to shown to various FTH and min value heights, so it is not linear (hence the shape is a bit different from the normal ones). Later I'll write a program to calculate it all at every 100 feet or so to give nicer charts.
Plus all numbers can move +/- 1% or so because I am converting charts to numbers for calculations.


But the results, I was bemused by them (so I double and triple checked them, no guarantee of course, if anyone finds an error please let me know and I'll fix it).
The 190D was developed as an interim design to give better high level performance to the 190. Needed for interceptions of the USAAF bombers and escort fighters.
The 213A was chosen for this, but the 801D was superior or equal in that 20,000-30,000ft region. Only at 35,000ft does it pull ahead and not by much.

At low altitudes the Jumo appears more powerful (but has that funny 'defying the laws of physics' shape again) up to about 17,000ft (more with MW-50 of course).

And yet this was supposed to improve high altitude performance?

Starts to explain why the 190D performance numbers, without power boosting, were not that great (still good though).

Any ideas anyone?


Nice thing about this, once I have written my program (those numbers were just done in Excel), is that later I will be able to overlay all sort of different engines.

Tante Ju said:

I often wonder why never been an "evaluation" of 109F and Spit 5 on ww2performance site. I guess Mike was not yet able to find bad enough graphs for 109Fs... Seriously, the bias of those articles are legendary in aviation community.. the errors (manipulations?) are well known.

The originals are good though. I prefer to read those and ignore these silly articles completely. I am sure everybody can find in originals what is interesting for him.

Click to expand...

And you should thank him for the work he has done in providing them. While, politely, disagreeing with his analysis and interpretations.
I think that is only fair, given the (obviously) tremendous work he has put in.
Nothing wrong with saying " I disagree, I think based on these numbers such is such", not so good to claim "bias", manipulation" or "silliness".

Hey, here is an opportunity for you .. you write an 'evaluation' of the Spit V vs the 109F, with all supporting materials of course (original sources only).
Naturally we will all agree or disagree "politely" of course, naturally no one will accuse you of "bias", manipulation" or "silliness".

I like honest analysis. I have my own personal disagreements with some of Mike's analysis, but I truly respect the work he has done, and the honesty of providing all the material.
If I have an issue that I care a lot about then I will contact him directly. Perhaps you should do so too.

I will not ever go behind his back saying anything about him , except "I respectfully disagree, this is what my analysis shows"..

Now the Jumo 213A numbers, taken from charts shown here with no MW-50 or GM1, but at 3,250 rpm, thus basic maximum power numbers without power boosting.
I assume they include ram air, but then again? Confirmation from anyone would be nice. If they are static then the correct comparison would be with the 801 static (or climbing) numbers.

Click to expand...

Your calculation is without ram air as you can see at Denniss graph.
The graph from Denniss shows (only) the performance with ram air for "Steig und Kampfleistung" (3000rpm). The red marker.



So you have a poweroutput/performance of 1480PS at 22300ft with normal "Steig- und Kampfleistung" at 3000rpm.

Edit:

Here the graph for the BMW 801D with ram air and normal Steig- und Kampfleistung at 2400 rpm


So you have a poweroutput/performance of 1320PS at 19600ft with normal "Steig- und Kampfleistung" at 2400rpm.

Now you can see, why the FW190D-9 was a major improvement for higher altitudes.

Hello, OldSkeptic. Some remarks:

OldSkeptic said:

...
I took various 801D numbers (all at max settings without C3).

Click to expand...

The would be 'without C3 acting as anti-detonant'?

Two sources agreed well. The USAAF tests, which I think were on a static rig to NACA specs. There are 2, with and without the geared fan.
These agree quite well with FW's own climbing numbers, that is without any (or minimal) RAM air.
The FW numbers are on level flight, that is with ram air increasing boost. This increases power and delays FTH.
I suspect the very high altitude ones (30,000ft+) are a bit high, because by that point IAS would be getting very low.

Click to expand...

The lines for engines with ram and without fan would just throw more confusion IMO.
Here is the BMW 801D chart, it, conveniently, has altitude expressed in ft. Thick lines are for static engine. The lines are for figures without fan, subtract 100-50 PS to get real power available to the prop (as from table attached below).

...
Basically the BMW numbers look good, excepting the very high altitude with ram air, and overall cross check quite well.

Click to expand...

If you will be so kind to make another chart (containing the data posted above, and without ram take into account), we might get a slightly different results. The results at high altitude would be comparable, both engines were single-stage anyway.

Now the Jumo 213A numbers, taken from charts shown here with no MW-50 or GM1, but at 3,250 rpm, thus basic maximum power numbers without power boosting.
I assume they include ram air, but then again? Confirmation from anyone would be nice. If they are static then the correct comparison would be with the 801 static (or climbing) numbers.

Click to expand...

As noted from DonL, all lines are for static engine, bar the lines highlighted in red by him.

Now I took the numbers at min/max values and back calculated the in between ones, to enable like by like comparisons.
PS is corrected for to BHP. KM to feet.
The X-axis is chosen to shown to various FTH and min value heights, so it is not linear (hence the shape is a bit different from the normal ones). Later I'll write a program to calculate it all at every 100 feet or so to give nicer charts.
Plus all numbers can move +/- 1% or so because I am converting charts to numbers for calculations.

Click to expand...

Okay.

But the results, I was bemused by them (so I double and triple checked them, no guarantee of course, if anyone finds an error please let me know and I'll fix it).
The 190D was developed as an interim design to give better high level performance to the 190. Needed for interceptions of the USAAF bombers and escort fighters.
The 213A was chosen for this, but the 801D was superior or equal in that 20,000-30,000ft region. Only at 35,000ft does it pull ahead and not by much.

At low altitudes the Jumo appears more powerful (but has that funny 'defying the laws of physics' shape again) up to about 17,000ft (more with MW-50 of course).

And yet this was supposed to improve high altitude performance?

Click to expand...

The (not only high altitude) performance was improved, not because the Jumo-213A was an uber engine, but because it was offering two important things - less drag and better use of ram effect. We can note that, even the 190A-9, with improved BMW-801S, way paying the price in drag, and with more HP it was slower than D-9. It was also featuring the internal air intakes (= less able to capitalize on ram effect), a major handicap for fights above 20000 ft.
The 190A, when tested with external intakes, was found to be faster at high altitudes than the regular 190A with internal intakes.

Starts to explain why the 190D performance numbers, without power boosting, were not that great (still good though).
Any ideas anyone?

Click to expand...

I guess you speak about 190D-9? That one was flying with engine featuring single stage engine, and any good plane with two stage engine will be faster climb better where the air is thinner (=hi-altitude), no sweat.

Another thing where the 213A was better than 801 was exhaust thrust - static engines were making, eg. at 7km, 126 kg vs. 100 kg of exhaust thrust. Or, 150kg vs. 125 kg at ~5,5 km. Also, the D-9 was having 2 cannons less, along with 2 ammo chutes less - less drag.

Also note thas all graphes from the Jumo 213A/E except the one from Denniss shows performance datas without ram air.

The graph from Denniss shows also exactly which exhaust thrust (kg)was generated from the Jumo 213A, with which outputperformance (Sondernotleistung, Start/Notleistung and Steig- und Kampfleistung)

Thanks for all that everyone, I'll update. Yep, makes a lot of sense about the drag issues and exhaust thrust being a factor.

Until something more professional looking is posted, here is my contraption - the red line is for Jumo 213A from the graph Denniss kindly posted, the blue line is for BMW 801 based upon the values from the table from post #49. The 100 PS difference above 5,7 km is apparent. Denniss' chart also nicely shows that 213A can add another km to the critical altitude via taking advantage of ram effect, the 'regular' 801 fares less well in that area.

Tomo ist this for static engine or with ram air?

Because I think Start/Notleistung with ram air (Jumo 213A) would be much smoother and better at higher altitudes?

My interpretation of the Jumo 213A with Start/Notleistung and ram air, taken from the chart with Steig and Kampfleistung.



Edit I see you have already answered my question

On the 801 the fan was consuming 70-80PS at 2700rpm and down to 20-30PS at 2000rpm, varied a bit with engine version. BMW graphs show 25-70 for the 801S/TS and 20-82 in the 801Q/TU

70-80 PS to drive a fan...?! Seems unbelievable.

That's only 4%. My old 1966 427 big block Chevy mechanical fan uses about 25hp @ 4800rpm. That's 6%.

Denniss has posted the graphs covering that here.

tomo pauk said:

Denniss has posted the graphs covering that here.

Click to expand...

Thank Tomo, its hard to believe at first but its there on the graph, black and white!

Thanks also altsym. I did not know even cars "waste" so much power on driving a fan... thats something like 18 000 Watt for a car fan... what sort of electric motor is that and why does it need to be so powerful?

"Thanks also altsym. I did not know even cars "waste" so much power on driving a fan... thats something like 18 000 Watt for a car fan... what sort of electric motor is that and why does it need to be so powerful?"

Up until the 1980's automobile engines had fans that were operated via a belt drive running off of the engine crankshaft. The problem was that a fan that was configured to provide adequate cooling for an idling engine in a stationary vehicle took a considerable amount of power when the engine was operating at a speed corresponding to its rated output or anything close to it, even though the flow of cooling air resulting from the vehicle motion would have been more than sufficient. Consequently, newer vehicles have a thermostatically controlled electric motor driving the fan. This arrangement only operates when needed and gives a significant improvement in net engine output and overall efficiency.