Jump to content

sea-level engine vs. altitude engine


ACEOFACES
 Share

Recommended Posts

 

 

Well, most countries make two different versions of military equipment when they sell it to other countries.  One is an export version and the other for domestic use.

 

Why was it called a P-400 and not a P-39?

 

 

p400.jpg

 

 

 

Proper supercharging equipment?

 

What engine was used in the P-51 and Mustang I?

Link to comment
Share on other sites

Proper supercharging equipment?

 

What engine was used in the P-51 and Mustang I?

This only means that compared with the Navy's F4F-3/4 Wildcats which had two-speed superchargers rated for higher altitudes, the P-400's single speed supercharger rated for lower altitudes was inferior: The last sentence reads  "As a consequence the high-scoring honors on Guadalcanal easily passed to the Marines in their rugged and effective Wildcats." Must have been embarrassing to the USAAF to have to give kudos to the USN.

 

http://www.wwiiaircraftperformance.org/f4f/f4f-4.pdf

 

Nothing to do with the engines in the P-400s being sea level rated, nor has there any evidence been posted to say that just because boost control wasn't fully automatic it wasn't a boost control mechanism as required by an altitude supercharger.

 

Evidence = not anecdotes about modern civilian standards and practices, not opinion.

Edited by NZTyphoon
Link to comment
Share on other sites

.

Proper supercharging equipment?

Yes proper supercharging can mean a lot of different things to different people..

 

With regards to the book Crump quoted, i.e. THE ARMY AIR FORCES in WWII dated 1983

 

The first thing to point out is the statement 'proper supercharging' should not be confused with 'no supercharging' as Crump is trying to imply again..

 

Which is easy to show even from this current reference..

 

In that if that was the case.. How is it these P-400s have a critical altitude near that of the P-39 value of 10,300ft? i.e.

 

.

THE ARMY AIR FORCES in WWII

pilots were forced to do their flying at low levels, usually below 10,000 to 12,000 feet

Also take note of the reference to 'export version' i.e.

.

THE ARMY AIR FORCES in WWII

As an export version of the early P-39 originally destined for the British

Where Crump points to that quote and than asks

 

'Why was it called a P-400 and not a P-39?'

 

As if to imply the reason was because Allison made two different versions of the V-1710E4 (-35) engine..

 

Once again, Crump has shown how little he knows about the P-39/P-400!

 

It is easy to find out what made the P-400 different from the P-39..

 

The main reason being the P-400 had a 20mm cannon in place of the 30mm cannon..

 

There are other small changes too, one of which is mentioned right in the reference Crump provided where it made note of the oxygen bottles..

 

Just a little research will show you there were other little differences..

 

But no where will you find anything that implies let alone indicates that the V-1710E4 (-35) in the P-400 was any different than the V-1710E4 (-35) in the P-39 from the same time period..

 

Yet that is what you would have to 'want to' belive for anything that Crump has said to make sense..

 

As for what the author meant by 'proper'..

 

One only has to read a bit further to understand, i.e.

 

.

THE ARMY AIR FORCES in WWII

pilots were forced to do their flying at low levels, usually below 10,000 to 12,000 feet or less than half the altitude of the attacking bombers

Crump has provided no new information here..

 

Apparently it is new to him, but not to those who know anything about the P-39/P-400! In that I think it is safe to assume that most, if not all, people reading this post knew the P-39/P-400 was not a high altitude fighter.

 

I also think it is safe to assume that most if not all of the people involved in this thread agree that the V-1710E4 (-35) engine meets the definition of an 'altitude engine'..

 

Crump being the clear exception here!

 

I don't think the definition can be made any clearer than it already has been made!

 

Thus at this point, the forum reader had to choose who to belive..

 

The documented definitions and the majority here.. Or Crump's personal definitions and his lone opinion..

 

But before the readers makes that choice

 

I should point out that when this conversation stated..

 

Crump was under the impression that the P-39/P-400 engines were NOT supercharged at all!

 

That is to say Crump was under the impression that the engines used in the P-39/P-400 were naturally aspirated engines!

 

Thus one would be wise to take pause before believing anything Crump has to say wrt the P-39/P-400.. But I digress.

 

A belief that was quickly pointed out to be wrong!

 

Something Crump never really took credit for and basically blamed the people/authors he was quoting, who were wrong, as to why he was wrong.

 

Which most find odd in how someone of his self proclaimed background and experience was doop by these author with regards to such a basic subject of aviation.

 

The good news is at that point Crump changed his tune and proceeded to say that, even though the P-39/P-400 engines are supercharged.. Which is his way of admitting he was wrong.. They are of the early 1:1 ratio sea-level type supercharger.. Which is his way of trying to say he was kind of right..

 

An early sea-level supercharger where the power is indeed more than the naturally aspirated engine, but power drops off stating at 'sea level' just like a naturally aspirated engine.

 

Since that statement by Crump, several people have pointed out that statement by Crump is also in error..

 

One only has to look at the test results of the eight different P-39 tests I provided to see the power does NOT drop off starting at sea level..

 

More intuitively one can see in those eight tests that each makes note of a 'critical altitude' that is well above sea level..

 

At which point one only has to ask, how does a sea-level engine have a critical altitude above sea-level? It's simple!

 

By definition it cant! ;)

 

.

Evidence; not anecdotes about modern civilian standards and practices, not opinion.

Agreed 100%

Edited by ACEOFACES
Link to comment
Share on other sites

 

I also think it is safe to assume that most if not all of the people involved in this thread agree that the V-1710E4 (-35) engine meets the definition of an 'altitude engine'..

 

What definition is that??

 

 

The CFR 14.1 part 1?

 

 

 

 

Sea level engine means a reciprocating aircraft engine having a rated takeoff power that is producible only at sea level.

 

 

 

 

 

http://aviationglossary.com/sea-level-engine-14-cfr-1-1/

 

 


 

 

 

The P-400 as tested by the RAF is a sea level engine.  That is a fact.

 

 

allison1710e4ratings.jpg

 

http://www.wwiiaircraftperformance.org/P-39/AH573.pdf

 

 

 

 

Edited by Crump
Link to comment
Share on other sites

The maximum boost obtainable at sea level with an V-1710.E.4 engine was ~61", producing around 1600 hp.

 

This was put to good use later in the war, when the V-1710.E.4 received a war emergency rating of 56". This rating had a critical altitude of 3500' no ram. The engine developed 1470 hp at sea level and 1520 hp at 3500'. It gave the aircraft a top speed of 335 mph at sea level and 363 mph at 6000'.

Edited by JtD
Link to comment
Share on other sites

This was put to good use later in the war, when the V-1710.E.4 received a war emergency rating of 56". This rating had a critical altitude of 3500' no ram. The engine developed 1470 hp at sea level and 1520 hp at 3500'. It gave the aircraft a top speed of 335 mph at sea level and 363 mph at 6000'.

 

 

 

Does not have anything to do with the RAF P-400, does it?

 

I am sure the engine was developed and improved but that is not the topic.

Link to comment
Share on other sites

 The British Airacobra was virtually identical to the American P-39D, but the slower-firing 37-mm cannon was replaced with the faster-firing and more reliable Hispano 20-mm cannon with 60 rounds. Two 0.50-inch machine guns were mounted in the fuselage, and four 0.30-inch machine guns were mounted in the wings. The engine of the Model 14 was the 1150 hp Allison V-1710-E4 (-35).

 

The USAAC even tested a P-39D with such a weapon load.

http://www.wwiiaircraftperformance.org/P-39/P-39D-FS-M-19-1521-A.pdf

Link to comment
Share on other sites

 

virtually identical

 

 

So that means the same, huh?

 

Why call it a P-400 at all?  Maybe because it was a way to keep track of the export models on the assembly line and the differences?

Link to comment
Share on other sites

p39v171035.jpg

 

 

Now I suppose all the baloney will start again.  We will have some reason why the 14 CFR 1 part 1 does not apply and somebody will focus on the power being the same despite the fact the manifold pressure and rpm are different.  They raised the rpm limit to compensate for the superchargers reduction in manifold pressure to keep the power the same.

 

It has nothing to do with the supercharger being able to maintain redline manifold pressure.

 

The Allison V-1710-35/E4 is a sea level engine at the time the RAF purchased the P-400.

 

Notice, Nztyphoon, the "critical altitude" for the highest manifold pressure the supercharger could develop is clearly labeled "sea level".

Link to comment
Share on other sites

The maximum boost obtainable at sea level with an V-1710.E.4 engine was ~61", producing around 1600 hp.

 

This was put to good use later in the war, when the V-1710.E.4 received a war emergency rating of 56". This rating had a critical altitude of 3500' no ram. The engine developed 1470 hp at sea level and 1520 hp at 3500'. It gave the aircraft a top speed of 335 mph at sea level and 363 mph at 6000'.

Thanks JtD!

 

This info is relevant to the discussion in that it does have to do with the RAF P-400 in that the P-400 has a V-1710.E.4 (-35) motor

 

Granted Crump would have us belive that Allison made more than one version of the V-1710.E.4 (-35)..

 

Where he notes that as time progressed Allison made improvements to the V-1710 'series' of engines..

 

Which is true!

 

But each time Allison made a change to an engine, they gave it a new model number..

 

Which can be seen here.

 

Allison V-1710 Motors

 

Anyone who has ever picked up a wrench and replaced a part on a motor knows how important it is that the motor makers keep track of the versions coming off the assembly line!

 

That is to say it would be very confusing if there were several different versions of the motor used in your car that all shared the same model number!

 

.

The British Airacobra was virtually identical to the American P-39D, but the slower-firing 37-mm cannon was replaced with the faster-firing and more reliable Hispano 20-mm cannon with 60 rounds. Two 0.50-inch machine guns were mounted in the fuselage, and four 0.30-inch machine guns were mounted in the wings. The engine of the Model 14 was the 1150 hp Allison V-1710-E4 (-35).

Thanks Milo!

 

That just confirms what most of us already knew going into this topic!

 

On that note, did you notice Crump's reply to you?

 

Where he says in so many words..

 

The reason they called the P-400 a P-400 and not a P-39

 

Is because it is very important to keep track of the differences between airplanes rolling of the assembly line!

 

Hunnn.. That is exactly what we have been saying about the Allison V-1710E4 motors!

 

How is it Crump can understand the importance of keeping track of the differences in two virtually identical airplanes such that they called one a P-400 and the other a P-39..

 

And than one post later expect us all to belive that Allison made changes to the V-1710E4 motor without changing the model number?

 

I mean it is one thing to flip flop in one thread from the next

 

But flip flop from one post to the next on the same page?

 

But I digress..

 

As most of us know, it is just as important to keep track of difference in the motors as it is an airplane!

 

Which is why Allison assigned a new model number for each change they made.

 

And is why the power settings used in a test of a P-39 with a V-1710-35 applies to a P-400 with a V-1710-35

 

And is why the V-1710-35 used in a P-400 is a altitude engine

Edited by ACEOFACES
Link to comment
Share on other sites

The V-1710.E.4 developed more power at 2800rpm than at 3000rpm, if the manifold pressure was the same.

 

Of course, as it would in any engine.

 

What does that have to do with the fact the V-1710E4 in the P-400 is a sea level engine?

Link to comment
Share on other sites

Sea level engine means a reciprocating aircraft engine having a rated takeoff power that is producible only at sea level.

 

Where does it say the rpm and boost have to be the same? All that is mentioned is power, not how the power was achieved. 

Link to comment
Share on other sites

Sea level engine means a reciprocating aircraft engine having a rated takeoff power that is producible only at sea level.

 

Where does it say the rpm and boost have to be the same? All that is mentioned is power, not how the power was achieved. 

It doesn't Milo. Going back to the N.T.I book on aircraft power plants and how to convert a sea level supercharger to an altitude unit:

 

Sealeveltoaltitude_zpsa8e2de7f.jpg

Note the comment "a slight degree of overboosting is sometimes used to obtain extra power for emergencies." Nowhere is it stated that the take-off rating has to be X hp at Y rpm and Z manifold pressure - these so-called "criteria" are window dressing, no more.

 

All that is needed is a gear that drives the blower (impellor, in British terms) at high speed and a boost control device, which could be anything from a stop on the throttle lever to a fully automatic boost control. The V-1710-E4 has both:

 

1-Airacobra-page-0012_zps80755cc6.jpg

the blower is driven at 8.8 times engine speed. This is why it is called a single-stage, single-speed altitude supercharger

 

Also, we are talking about late 1930s - early 1940s military technology and definitions, not modern civilian aero engines and definitions.

Edited by NZTyphoon
Link to comment
Share on other sites

Where does it say the rpm and boost have to be the same?

The only place you will find constant RPM and Manifold pressure used in the definition of a sea-level or altitude engine is in one of Crump's 'personal definitions' of a sea-level or altitude engine.

 

NO WHERE ELSE!

 

The first time Crump tried to use his 'personal definition' in place of the actual definition was after I posted the eight test examples of a P-39 with V-1710 engine having a rated takeoff power that is producible from sea level to an established higher altitude

 

To which Crump responded with..

 

.

Not at a constant manifold pressure and rpm

At which point one has to question everything and anything he as to say on the subject..

 

Also note, it depends!

 

If Crump thinks the actual definition I provided will help his argument, he will use it! If he thinks it will hurt his argument, he will use his ever changing with the wind 'personal definitions'

 

.

All that is mentioned is power, not how the power was achieved.

Exactly!

 

Which is why his latest 'personal definition' of saying an altitude engine has to have a boost control to be an altitude engine is also incorrect.

 

Twice now Crump has tossed his 'personal definition' against the wall to see if they stick..

 

And twice they have hit the floor..

 

Thus one can only wonder what Crump will toss up onto the wall next?

 

I know it is hard to follow what Crump is saying, what with all the flip flops and flat out reversals..

 

But here is the sequence of how Crump's 'statements' have evolved with time..

 

No 1) Crump said the P-39/P-400 V-1710-35 engines were NOT supercharged at all.

A statement that was quickly proving to be in error..

 

At which point Crump moved onto his modified statement No. 2, i.e.

 

No 2) Crump said the P-39/P-400 V-1710-35 engines are sea level engines.

A statement that was quickly proving to be in error..

 

NOTE at this point..

 

Crump is no longer saying the V-1710-35 engines were NOT super-charged!

 

At which point Crump moved onto his modified statement No. 3, i.e.

 

No 3) Crump said just the P-400 V-1710-35 engines are sea level engines.

A statement that was quickly proving to be in error..

 

NOTE at this point..

 

Crump is admitting the V-1710-35 engines used in the P-39s are 'altitude' engines!

Crump is saying the V-1710-35 engines used in the P-400s are 'sea level' engines!

 

For this to make sense you have to..

 

1 - Belive that Allison made two different versions of the V-1710-35 engine.

2 - Ignore the fact that the RAF climb test was performed at a lower RPM setting than the US climb test.

3 - Ignore the fact that the US climb tests showed the rated takeoff power of 1,050hp was producible from sea level to an established higher altitude of around 10kft+

 

If you are able to belive/ignore all these things at the same time..

 

Than and only than can Crump's argument make sense..

 

.

Edited by ACEOFACES
  • Upvote 1
Link to comment
Share on other sites

 

 For reciprocating engines, ratings and operating limitations are established relating to the following:

(1) Horsepower or torque, r.p.m., manifold pressure, and time at critical pressure altitude and sea level pressure altitude for???
Link to comment
Share on other sites

What is amusing is some of you are treating this like it is some detrimental trait for an aircraft engine to be a sea level engine.

 

It does not make much difference at all whether an engine is sea level or an altitude engine.  A sea level engine with the same blower ratio can produce the same power as an altitude engine.  The pilot just has to manually control his manifold pressure as he changes altitudes.

 

You can see that on the V-1710E4 limitations.  The pilot just has to adjust his manifold pressure and rpm to maintain power.  In a climb, he has to advance his manifold pressure to keep it from falling.

 

It is not the big deal you guys are making.

Link to comment
Share on other sites

Allison Service School Handbook for V-1710 Aircraft Engine, 1943)

 

 

Hey guy,

 

Read the manual.  the engines were converted later in the war by the addition of the overboost controller.

 

 

They did not start out as altitude engines and the only difference was the location of the propeller reduction gear case.

Edited by Crump
Link to comment
Share on other sites

New information just to hand: (Allison Service School Handbook for V-1710 Aircraft Engine, 1943)

 

Allison19432-001a.jpg

 

 

That is worth repeating!!

 

all other "F" and "E" engines are altitude rated engines (horsepower rated at altitude)

 

In light of this information

 

I think we can safely say this does end the debate!

 

Again! ;)

 

 

Edited by ACEOFACES
Link to comment
Share on other sites

Just in case there is any confusion - the likes of the -35(E4) were not fitted with auto boost control:

 

Allison V-1710 Operation and Maintenance Manual 1944:

 

Allisonopanmain1944-002.jpg

No mention of the -35(E4) being fitted with ABC.

 

As it is stating as "fact"  an engine needed to be fitted with ABC before it could be rated as an altitude engine is completely erroneous - posting regulations and anecdotes about modern, civilian practices has nothing whatsoever to do with WW 2 military technology.

 

Edited by NZTyphoon
Link to comment
Share on other sites

As it is stating as "fact"  an engine needed to be fitted with ABC before it could be rated as an altitude engine is completely erroneous

Agreed 100%

 

As for Crump's latest attempt at redefining the definition of an altitude engine..

 

Saying an airplane has to have a boost control to obtain the rated takeoff power that is producible from sea level to an established higher altitude..

 

Is like saying my car has to have cruise control to obtain 60mph on the highway..

 

Because manually stepping on the throttle to obtain 60mph on the highway produces a 'fake' 60mph on the highway..

 

Yeah.. try telling/selling that one to the judge the next time you get a speeding ticket! ;)

Edited by ACEOFACES
Link to comment
Share on other sites

These are the genuine sea level rated Allison V-1710s:

 

Allison19432-002.jpg

 

Note the "F-21 Series", which includes the V-1710-87 fitted to the A-36:

 

AllisonV-1710-39F3Ra.jpg

 

Developed from sea level rated engines developed for the P-38, but in the A-36 without turbocharger, Critical Altitude = 5,400 feet Military (Mil.)

V-1710-395b-2.jpg

 

cf 12,000 ft Mil. or 10,800 Normal (Nor.) rated for the V-1710-35 aka V-1710-E4

 

V-1711a.jpg

Link to comment
Share on other sites

Good Stuff NZ

Hey.. Do you remember that V-1710-33 chart Crump posted early on?

The one he said was proof that the V-1710 engines were un-supercharged sea-level engines?

Have you also noticed that he has not referred to that chart in some time?

Well, I thought I would take another look at that chart..,

 

Because something never seemed right about it, beyond what he was saying it proved.

Granted, it is a very hard chart to read! But I took the time to zoom in and I realized he was reading this chart all wrong!

Turns out this chart actually proves what we have been saying all along!

 

And it also confirms what was said in the NORTHROP AERONAUTICAL INSTITUTE AIRCRAFT POWER PLANTS document you provided.

 

Where it talks about the ability to over boost a powerplant that does not have a boost control, or one that allows the pilot to disable it, i.e.

 

NORTHROP AIRCRAFT POWER PLANTS
The chart shows that the power output at take-off, and for the first few thousand feed of climb, is less than that provided by the sea-level engine, but this does not mean that it is impossible to obtain greater horsepower at the lower levels. If the controls were removed and the engine operate with the throttle wide open, more power would be obtained. For example, at 10,00 ft., a condition of 'over boosting' would exist and there would be 115-hp. output. Likewise, at sea level, the theoretical power output would be about 1600 hp


Now take another look at that V-1710-33 chart, i.e.

V_1710_33_MIL_RATING.jpg

Note I zoomed in and type in the manifold numbers, and some of the text in blue.

Than I colored in the two power setting lines where..

The red line showing 38.# HG @ 3000 RPM
The green line showing 35.5 HG @ 2600 RPM


Than I added a line in yellow that extends from the rated horse power of 1150 hp back to the 3000 RPM Line.

And note, that yellow line passer right by the 44 Hg mark!!

Note, I am not saying this -33 is rated for 1150 hp!

I only added the yellow line to show -35 rated take-off value (~1150 hp ~44 Hg ) on this graph as a reference.

In summary, I think it is safe to say this debate is OVER!

Especially when the data the other side thought supported their claim..

Turns out to support our claim upon closer inspection! ;)

Edited by ACEOFACES
Link to comment
Share on other sites

That's much clearer; the original was so badly garbled I wondered what the point of it was in the first place. On closer examination some important detail was missed or overlooked.

 

Here are some further clarifications:

 

V_1710_33_MIL_RATING-1.jpg

 

Normal Rated Altitude = 12,000 ft, similar to the ratings for later V-1710s. Normal Rating @ Sea level - 840 (?) B.H.P @ 35.0 HG @ 2,600 R.P.M. Normal Rating @ 12,000 ft - 860 B.H.P @ 35.0 HG @ 2,600 R.P.M ie: the power curve goes up to rated altitude 12,000 ft.

 

(The original, for comparison)

 

allisonsupercharger1.jpg

Link to comment
Share on other sites

Nice Work N!

 

You got better eyes than I have! ;)

 

The contrast between the two is amazing!

 

It tells a completly differnt story now from what we were initally told!

Link to comment
Share on other sites

As it is stating as "fact" an engine needed to be fitted with ABC before it could be rated as an altitude engine is completely erroneous

 

 

No, that is the determining factor. 

 

 

No mention of the -35(E4) being fitted with ABC.

 

 

Depends on the time frame.  Early in the war, I don't believe it came with one but I am sure it was retrofitted with one as a WEP rating is not allowed in Allison engines without one according to the overhaul manual.

 

- posting regulations and anecdotes about modern, civilian practices has nothing whatsoever to do with WW 2 military technology

 

 

The regulations in place today are very close to the ones in place back then as they stem from the same conventions.

 

They legal basis was the same back then.

 

Only thing is today the CFR is more developed.  Such things as standard definitions have been adopted.

 

Tagert,

 

The engine cannot hold manifold pressure at red line...that is a sea level engine.

 

Look at an altitude engine chart, it has no such line because it is equipped with an overboost controller.

Link to comment
Share on other sites

Wouldn't an over boost contoller be the relief valve on the supercharger?

The relief valve is part of it - but I wouldn't worry.

 

So far Crump has not provided any actual WW 2 vintage documentary evidence to support his belief that WW2 military engines required ABC before they could be rated as altitude engines, so whatever argument, he has, based on anecdote and modern civilian regulations, is shaky and circumstantial at best.

 

I don't see why everyone else should continue to do all the hard work and research while Crump just sits there and carps.

Link to comment
Share on other sites

 

Nztyphoon says:

 

shaky and circumstantial at best

 

 

Thanks for putting a smile on my face this morning! 

 

1.  The V1710E4 as delivered to the RAF in the P-400 in 1941 fits the definition of a sea level engine in every way.  It's power drops off with altitude at red line, the sea level take off rating is not producible at altitudes above sea level, and it perfectly fits the 14 CFR Part 1.1 definition of a sea level engine.

 

Looks like a duck, walks like a duck, it probably is a duck.... ;)

 

2.  All the arguments against that are based on 1943 and 1944/45 engines.  All arguments based on this data are circumstantial.  The only hard evidence we have is the engine limitations of the P-400 as tested by British.  Those engine limitations clearly define the engine as delivered by Allison to the RAF as a sea level engine.

 

3.  Allison started the war without the best supercharger's around and worked continuously during the early periods to improve their supercharger designs and technology.

 

http://www.enginehistory.org/Convention/2009/Presentations/SuperchargingAllison.pdf

 

 

Let's see what we know.  The evidence is pretty strong that Allison's fitted an overboost controller that could be mounted in various installations to turn their supercharged engines into altitude engines.

 

1.  The Manifold Pressure Regulator is the difference between a sea level engine and an altitude engine.  In its most basic form, a sea level engine will not maintain manifold pressure with an increase in altitude.  As the engines climbs in altitude, the manifold pressure falls off.  Below red line, the pilot can increase throttle to maintain manifold pressure but that does not change the fact a sea level engine will not hold manifold pressure with a change in altitude.

 

An altitude engine will hold manifold pressure with a change in altitude.  The pilot does not have to keep manifold pressure as the engine will automatically maintain whatever manifold pressure he sets up to critical altitude.

 

This is also reflected in Allison's Overhaul manual from 1943:

 

1.  Allison gives clear instructions on the operational differences in the engines equipped with an automatic manifold pressure overboost controller and the engines not equipped with one.

 

manifoldpressureregulat.jpg

 

 

 

2.  The overboost controller was not present on all Allison engines of the same type.

 

In the 1943 Overhaul manual it clearly states that War Emergency Power is not authorized on any engine that does not have a boost controller.  It is the War Emergency Power rating which meets the definition of CFR Part 1.1 for an altitude engine.  All Allison engines with WEP produce more horsepower at altitude than the take off rating at a higher manifold pressure.

 

automaticmanifoldpressu.jpg

 

The take off rating instructions are clearly noted in the overhaul manual when the engine is equipped with an automatic manifold pressure regulator, cleared for WEP, and the warning about the automatic manifold pressure regulator is re-emphasized.

 

takeoffratingandwep.jpg

 

 

Allison kept track of the installation of the automatic pressure regulator in their engine designs.  Here we have a portion of a document noting the differences between P-40 Tomahawks. 

 

overboostcontrolleralli.jpg

 

Here we see the differences in the ratings allowed for the V-1710-81 engine when equipped with an automatic manifold pressure regulator. 

 

waremergencypowerandove.jpg

 

Power production at WEP when equipped with automatic manifold pressure regulator:

 

weppowerv171081.jpg

 

http://www.wwiiaircraftperformance.org/P-40/P-40N_42-9987_FS-M-19-1535-A.pdf

 

Without the automatic manifold pressure regulator, the Allison V-1710-81 is a sea level engine according to 14 CFR Part 1.1.  The take off engine setting is not reproducible above sea level and the engine will not independently maintain manifold pressure with an increase in altitude. Clearly a sea level engine....

 

With the automatic manifold pressure regulator, the Allison V-1710-81 meest the 14 CFR Part 1.1 definition of an altitude engine.  The engine can produce a manifold pressure higher than the take off power setting resulting in higher horsepower at altitude than sea level, and the engine can independently maintain manifold pressure with an increase in altitude.  Clearly an altitude engine.....

 

In conclusion, Allison improved their superchargers during the war.  One such improvement was the introduction of an automatic manifold pressure regulator which could be fitted to the engines in a number of different installations converting a sea level engine into an altitude engine.  Using late war data from 1943/44/45 tells us nothing about an early war variant Allison engine.  The only evidence we have so far the directly speaks to the engines the RAF recieved in their P-400 is the engine limitations in the British trials of the P-400.

 

The engine in the P-400 as delivered and tested by the British clearly meets the 14 CFR Part 1.1 definition.   The highest manifold pressure allowable is the take off rating.

 

allison1710e4ratings.jpg

Link to comment
Share on other sites

The P-40M and N were equipped with exactly the same engine, both with an automatic boost control. The V1710-81 did not come without. If you have proven anything, then it is the quality of your contributions.

 

I would think the debate's run long enough. Allison says it's an altitude rated engine, Crump says it's a sea level rated engine. Nothing is going to change that. I guess everyone who cares (few enough for sure) can decide who they want to agree with.

Edited by JtD
Link to comment
Share on other sites

The P-40M and N were equipped with exactly the same engine, both with an automatic boost control. The V1710-81 did not come without. If you have proven anything, then it is the quality of your contributions.

 

I would think the debate's run long enough. Allison says it's an altitude rated engine, Crump says it's a sea level rated engine. Nothing is going to change that. I guess everyone who cares (few enough for sure) can decide who they want to agree with.

 While it's good to see that Crump has finally provided some documentary information most of it is of no use whatsoever in defining an altitude engine.

 

*All Crump's arguments against that are based on 1943 and 1944/45 engines.  All arguments based on this data are circumstantial. 

 

*As pointed out by JtD, Crump neglected to mention that all -81 series engines were fitted with automatic boost control, so these statements

 

Without the automatic manifold pressure regulator, the Allison V-1710-81 is a sea level engine according to 14 CFR Part 1.1.  The take off engine setting is not reproducible above sea level and the engine will not independently maintain manifold pressure with an increase in altitude. Clearly a sea level engine...

 

.With the automatic manifold pressure regulator, the Allison V-1710-81 meest the 14 CFR Part 1.1 definition of an altitude engine.  The engine can produce a manifold pressure higher than the take off power setting resulting in higher horsepower at altitude than sea level, and the engine can independently maintain manifold pressure with an increase in altitude.  Clearly an altitude engine.

prove nothing

 

* War Emergency Power or WEP is not used to define an engine's altitude rating because, as Allison state, using it places a huge amount of strain on the engine and must not be used, except in an...Emergency. 

AllisonWEP2a.jpg

*As this document states a WW2 engine was rated on it's  military power and the altitude to which that power could be maintained. The use of the modern 14 CFR regulations to define WW2 engine ratings is completely misleading.

 

*Where are the WW2 vintage regulations which stipulate that a supercharger must be fitted with Automatic Boost Control before being rated as an altitude engine?

 

*Allison's own interpretation of what engines were rated as sea level or altitude.

 

Allison19432-001a.jpg

 

*Not once did Crump demonstrate that all  E4/-35s, rated by Allison as an altitude engine, were routinely retro-fitted with ABC, thus, in his opinion, qualifying them to be altitude rated. The only engines fitted with ABC were:

 

Allisonopanmain1944-002.jpg

 

*Crump has ignored the 1948 Northrop Aeronautical Institute book which stipulates that to convert a sea-level rated engine to an altitude rated all that's needed is a higher blower gearing and some sort of boost control device - the book did not stipulate Automatic Boost Control was required. The latter is desirable because it is one less thing to worry about when in combat, but ABC is not absolutely needed.

Edited by NZTyphoon
Link to comment
Share on other sites

JtD says:

 

Crump says it's a sea level rated engine

 

 

 

 

All this insinuation this is my idea is intellectually bankrupt.  I am glad you edited your post, JtD.  It is not my definition, it is the definition of the Aviation Authority of the United States.  That definition conforms to international convention and is the standard for the vast majority of the aviation world existing on planet earth.

 

 

 

Each contracting State undertakes to adopt measures to insure that every aircraft flying over or maneuvering within its territory and that every aircraft carrying its nationality mark, wherever such aircraft may be, shall comply with the rules and regulations relating to the flight and maneuver of aircraft there in force. Each contracting State undertakes to keep its own regulations in these respects uniform, to the greatest possible extent, with those established from time to time under this Convention.

 

 

http://www.spacelaw.olemiss.edu/library/aviation/IntAgr/multilateral/1944_chicago_convention.pdf

 

 

Nztyphoone says

 

*Allison's own interpretation of what engines were rated as sea level or altitude.

 

Exactly.

 

 

Why did 14 CFR Part 1.1 adopt a standard definition for "sea level engine"? 

 

Prior to a standard definition being adopted, the manufacturer is the one who set their own definition.  So, if an engine manufacturer put a supercharger on their engine they could simply say, "An engine with a supercharger is an altitude engine" or whatever standard the company wanted. 

 

That standard defined the power setting at altitude must be equal too or greater than the power setting for take off.  As 14 CFR Part 33 tells us, that means the manifold pressure and rpm must remain equal too or greater than the take off rating in order for an engine to be an altitude engine.  

 

If you look under the cowling of a supercharged engine, the presence of some type of manifold pressure regulator/ pressure relief valve to maintain manifold pressure is the physical difference between the two types of engine, altitude and sea level.  Why? That is a requirement in order to increase pressure beyond what the engine is capable of doing at sea level.  If it is not present, then the pilot is at risk of killing himself on take off by being able to cause detonation thereby destroying his engine.

 

It is a simple law of physics called the combined gas law.  It tells us pressure, volume, and temperature are all linked in a gas.  Since the ambient pressure decreases with a gain in altitude, the supercharger must work harder to keep the same pressure.   In order to have a manifold pressure at altitude that exceeds what is tolerable on take off and does not cause detonation, we must have a way to reduce the excess pressure at low altitudes safely avoiding detonation.

 

That is the purpose of a manifold pressure regulator and why one is required on an altitude engine.  Without it, or manifold pressure drops with an increase in altitude.

 

 

We don't have make it so complicated.  If the manifold pressure drops off with an increase in altitude from sea level so that the pilot has to advance the throttle to maintain it, then it is a sea level engine.  It will meet the 14 CFR part 1.1 definition in every respect.

 

Pretty cut and dry.

Link to comment
Share on other sites

 

As this document states a WW2 engine was rated on it's military power

 

 

 

It does not say anything about Military Power.  It says the power is rated at altitude. 

 

Well, in the V-1710E4 from 1941 as tested by the RAF, the power sea level is the maximum power setting the engine produces representing the highest manifold pressure the supercharger is capable of safely producing.

 

You keep posting 1943/44/45 data as proof that a 1941 engine was the same. 

 

I don't think anyone who is knowledgable of the development and speed of innovation regarding piston engine powered aircraft engines from that period would think that determing the characteristics of an early war export model can be found by examing late war data of the country of origin.

 

Look at any of the data you have presented, all of the engines Allison says are altitude engines produce more power at altitude than they do at take off rating.  That is a characteristic of altitude engines.

 

What is factual is the engine ratings as tested by the RAF in 1941 conform to the 14 CFR Part 1.1 definition for a sea level engine.  It is not capable of maintaining manifold pressure and the same power settings above sea level.

 

Look closely at the approved power settings!!  How does it conform in any way to the definition of an altitude engine in 1941??  It does not, NzTyphoon. 

 

 

allison1710e4ratings.jpg

 

 

Pretty simple.

Link to comment
Share on other sites

Looks like a duck, walks like a duck, it probably is a duck.... ;)

Interesting..

 

Based on Crump's definition of an altitude engine..

 

The V-1710-35 (E4) used in the P-39s are NOT altitude engines..

 

Because the V-1710-35 (E4) did not have an automatic boost control..

 

But..

 

Based on FAA's definition of an altitude engine..

 

The V-1710-35 (E4) used in the P-39s are altitude engines..

 

Because the V-1710-35 (E4) is capable of providing rated takeoff power that is producible from sea level to an established higher altitude.

 

Note the FAA definition does not care how the power was achieved!

Be it due to the pilot adjusting the throttle manually

or

By some device doing it automatically..

 

It does not mater!

 

All that maters is if the engine can produce the rated takeoff power at higher altitudes..

 

 

At this point, the reader will have to decided who to belive

 

 

But before you decide, know this!

 

Crump initially thought the P-39/P-400 had NO supercharger at all, and were normally aspirated engines. i.e.

 

And normally aspirated engine. As an export variant, the P-400 was not equipped with a supercharger limiting its performance at high density altitude.

 

He later recanted (reversal) but as you can see his background and experience on the subject of supercharges is questionable from the start!

 

Later Crump provided a chart, i.e.

 

allisonsupercharger1.jpg

 

That he said is proof the V-1710 is a sea-level..

 

Now take a look at the same chart Crump provided where we colored in two of the test cases shown on the chart, i.e.

 

V_1710_33_MIL_RATING-1.jpg

 

  • The RED LINE shows the power per altitude at a constant manifold pressure of 38.9 Hg and a constant RPM of 3000 RPM.
  • The GRN LINE shows the power per altitude at a constant manifold pressure of 35.0 Hg and a constant RPM of 2600 RPM.

In both cases the power INCREASES with and INCREASE in altitude!

 

As in the curve/line moves up (Y axis) as the curve/line moves from left to right (X axis)..

 

Until it reaches the critical altitude, than and only than does the power begin to decrease!

 

Now lets take a look at what Crump had to say about the chart..

 

I am sure most of readers can examine the power charts below and see the trends in altitude performance at a constant manifold pressure and rpm. The Allison drops off with altitude while the BMW increases in power at a constant manifold pressure and rpm up to FTH. That is the basic difference between an altitude engine and a sea level engine.

 

Note Crump is saying the power DECREASES (drops off) with and INCREASE in altitude!

 

 

 

 

Which is not only wrong!

 

But just the opposite of what the power does with an increase in altitude! 

 

The strange thing in all this is

 

 

Crump was able to interpret the German BMW chart correctly..

 

Where he correctly noted the BMW power increases with an increase in altitude..

 

But, Crump was unable to interpret the American Allison chart correctly..

 

Why?

 

Your guess is as good as mine!!!

 

In the end, Crump in the only one that can answer that!

 

.

Edited by ACEOFACES
Link to comment
Share on other sites

All this insinuation this is my idea is intellectually bankrupt.  I am glad you edited your post, JtD.  It is not my definition, it is the definition of the Aviation Authority of the United States.  That definition conforms to international convention and is the standard for the vast majority of the aviation world existing on planet earth.

http://www.spacelaw.olemiss.edu/library/aviation/IntAgr/multilateral/1944_chicago_convention.pdf

 

Yet another smokescreen because this convention applies purely to civil, commercial operations: there's no mention of engine ratings or of how ratings were to be determined.

 

                                              Convention on International Civil Aviation,

Signed at Chicago, on 7 December 1944

(Chicago Convention)

 

Preamble

 

WHEREAS the future development of international civil aviation can greatly help to create and preserve friendship and understanding among the nations and peoples of the world, yet its abuse can become a threat to the general security; and

WHEREAS it is desirable to avoid friction and to promote that cooperation between nations and peoples upon which the peace of the world depends;

THEREFORE, the undersigned governments having agreed on certain principles and arrangements in order that international civil aviation may be developed in a safe and orderly manner and that international air transport services may be established on the basis of equality of opportunity and operated soundly and economically;

Have accordingly concluded this Convention to that end.

 

 

Where is there any mention of military law and conventions defining engine ratings during WW2?

 

 As 14 CFR Part 33 tells us, that means the manifold pressure and rpm must remain equal too or greater than the take off rating in order for an engine to be an altitude engine.  

 

If you look under the cowling of a supercharged engine, the presence of some type of manifold pressure regulator/ pressure relief valve to maintain manifold pressure is the physical difference between the two types of engine, altitude and sea level.  Why? That is a requirement in order to increase pressure beyond what the engine is capable of doing at sea level.  If it is not present, then the pilot is at risk of killing himself on take off by being able to cause detonation thereby destroying his engine.

 

 

Still no evidence or proof presented that ABC was a requirement by law for an altitude rated engine during WW2.

Link to comment
Share on other sites

Guest
This topic is now closed to further replies.
 Share

×
×
  • Create New...