rpm vs. man. pressure

[jodgi]

We're left with these ballpark estimations and guesstimations. HTC probably doesn't try to model engine performance too detailed it seems. I would love to see range increase with relaxed RPM and MAP settings, as it definately does in real life, but Soda's testing shows that (on the Tiffie) it doesn't. I haven't done any testing, but it seems to me that high alt cruising increases range (as it should). If you increase range by climbing at full performance and then glide, then it shows that we cannot expect high fidelity in AH's engine model. In real life this tactic wouldn't work - as a general rule.

It seems to me that the AH planes burn a lot of fuel on idle throttle. This leads to silly engine off gliding to conserve fuel. Anyone have any thoughts on this?

Real life prop AC "brake" quite a bit on throttle idle/max RPM. I don't know much of WWII AC in this regard, but I don't get a feel that it is very pronounced. Any thoughts?

Has anybody tested high versus low alt fuel consumption?
Can you wreck an engine by setting high MAP at low RPM?

Hmm, looks like i need to to some testing

Frankly, I haven't looked into any of this before reading this post. I simply found AH too simplistic (engine wise) to even consider it.

BTW: I've found massive help in your AC descriptions, Soda. Thanks for putting in so much "work" in them. (No pun intended, I just expect you enjoyed it too)

[Soda]

You're welcome.

My only tests on this were on the Typhoon so I don't know that those apply across all aircraft.  I haven't had a chance to run them on any other aircraft but I'm assuming that the results may be different (at least slightly).

I don't think this detracts from the game all that much though as fuel is easiler to judge in this fashion and people have created "fuel duration" images you can put in your clipboard to give you exactly the length of time your engine will run.  It's not like you need to lean out or reduce rpms in AH to travel very long distances 99.9% of the time.  If you are simply looking to extend your loiter time though you can simply cut throttle and it will improve your loiter time a lot.

[jodgi]

Agreed!

You guys just set me off;)

I think it is deliberate that the system, as it is now, is simple. Then there no learning curve on engine management on top of everything else. (I know I have my hands full on even basic ACM)

Where do I find the images you mentioned? Are they posted somewhere?

If you have stuff that is not included in your guides feel free to send it to me: dagfinn@start.no

I've made some simple and easy to read speed/alt XLS charts. Help yourself at netaces.

[MRPLUTO]

REDUCING MP & RPM WILL GREATLY INCREASE RANGE -- HERE'S HOW:

You first need to be at cruising speed at an altitude at which your engine gets good performance.  Then reduce MP (manifold pressure, or boost in UK) and RPMs.  You'll go much further than someone who uses full power.

*******

Here are some test results:

How far will I go on the notoriously small aux tank on a P-47D-11?

Fuel burn rate was 2, the same as in MA.  (At least that's what I've heard.)

Flight #1:

20k, entered course level at 245 mph IAS (indicated airspeed), dropped DT and hit WEP.  After WEP was used up I left if off.  WEP accerated the plane to just over 400 mph TAS (true airspeed) and then plane gradually slowed to 385 TAS.  This is in accordance with the flight charts from HTC.

Distance Flown:  82 miles


Flight #2

Same as above, but as I entered the course, I reduced the MP to 32.5 (65%) and RPMs to 2100.  The plane slowed gradually to 230 IAS, which at 20k meant my TAS was 310 mph.  I maintained this speed for the entire flight.

Distance Flown:  130 miles

*******

Range was increased by 59%.






MRPLUTO VMF-323 ~Death Rattlers~ MAG-33

[Isatheprophet]

Hi

With regards to rpms and what settings, in most ww2 aircraft the rpms beleow 2000 metres was set about 2000 -25000, higher above that the less rpms the plane needs to use, it is like going up a gear  in the car, Max rpms is 1st and the less you use the higher the speed, Yes in this context you will use less fuel and the engine will manage better. However one of the posts says fighters used to match the rpms with the bombers, to save fue. I do not think this is correct because  a fighter is alot faster than a bomber at high altidue.

Say a P51d was flying at 25k the rpms would be alot lower than at 6k and why this what gives the planes the speed and fuel effiecency. If the plane matched the bombers speed and rpms the engine would not perform at this attitude burn more fuel and proabably over heat eventually. The job of a fighter is to scan for enemy planes and some would follow the bombers in close formation but this was done sparingly and not for any length of time most fighers where abover the bombers, at hieght behind or front and they would be travelling on average about 350 + doing fighter sweeps on the look out for the hun from the sun.

[Gooss]

If manifold (throttle) is at maximum and RPM's less than maximum,  will the plane fly faster or slower than max RPM and max throttle?

HONK!
Gooss

(Yeah, yeah, I will test it next time online.  Just curious.)

[jodgi]

In real life too much MAP over to little RPM would overstrain the engine and eventually damage/break it. The exact settings for this would or will vary with different engines - this is not so in AH, the engines are indestructible... Unless you throw in shells

Generally, in real life, max speed is almost always attained with max RPM and MAP. In AH I think this is also so.

Compare it to rowing: Do I take many, quick and "light" strokes (?) or less but heavy strokes. Actually, if you're on a certain throttle setting and then decrease RPM, MAP will rise (on most engines). AH doesn't model these finer issues, and the only reason to fiddle with RPM would be to save fuel (I haven't tested this to be true) But it appears that some have found they can save fuel this way.

I do not think you will find a speed increase down the RPM road.

[Soda]

fyi,
  I ran additional tests on aircraft range/duration after my Typhoon tests.  I tested two other aircraft, the P-47D11 and P-38 though I didn't run a full set of settings numbers on either (I used a couple of generic rpm/throttle settings as compared to 100% values).  My results indicated that the P-47D11 had dramatic improvements ( in line with MRPLUTOs observations) though my P-38 numbers showed No improvements, in line with my Typhoon tests.  I can't claim these tests were foolproof but they seemed very strange as they were done using the exact same method in each case yet the P-47 showed the expected improvements while the P-38/Typhoon showed no improvement.

I know someone posted some "Actual" P-38 cruise settings at one point so it would be interesting to test those numbers out and see if it was an issue with the settings I used or whether some aircraft have a range/duration advantage at lower power settings.

-Soda
The Assassins.

[DamnedRen]

While all planes are different I found a good rule of thumb for gliding is expect 1k loss of altitude for each 1 mile covered with rpm at idle, engine off.

When I get carried away dogfighting (just have'n way too much fun) and notice I'm about outa fuel start a climb for home and immediately do a distance check to the nearest friendly field. Once I determine how far I gotta go     try and grab to the alt needed for the glide. If I gotta glide 10 miles I go for 10k minimum and I alwasy try to leave a lil gas in the tank for taxi to the hotpad. In most planes you will find you you arrive overhead your field with alt to spare.

However, you may want to check out your gliding distance in your favorite steed.

Ren

[MOSQ]

I tested the A-5. To my surprise it flew the exact same distance on WEP as on Cruise!

The test:
Climb to 10,000 ft on DT. Level out, let speed settle. At grid line drop the DT, go to WEP. Distance covered 3.2 sectors.

Repeat, but instead of WEP use the Max Cruise setting from the HTC Help pages for the A-8; 33"man @ 2100 rpm. Distance covered 3.2 sectors, but took 50% longer.

Lesson: In A-5 use WEP for home run. You'll cover the same distance, but when you run out of fuel you'll be going almost 100mph faster, therefore additional glide distance.

This is clearly not right. On cruise all planes should be able to fly  greater distances.

This also gives the P-47 another advantage in that it can "cruise" where other planes can't.

Historical Note on Charles Lindbergh regarding cruise settings from http://www.ww2pacific.com/lindbergh.html:

Republic had him test fly the P-47 Thunderbolt. United had him test the F4U Corsair. Working below the visibility of those in the upper Washington circles, he arranged to test the Corsair under combat conditions. Arriving at Guadalcanal, he showed how to take off with double the rated bomb-load and then showed that dive bombing with that load was out of the question, so he wiped out a gun emplacement with horizontal bombing.    
    MacArthur immediately heard of his unannounced arrival in the theater and ordered him to Australia where he was assigned to extend the range of the P-38 Lightning in New Guinea operations. Lindberg was able to return from combat missions with his tanks half full when others returned empty. He was able to teach how to add 500 miles to the P-38's range. It had been considered to be 400 miles, Lindbergh's techniques let the Lightning appear hundreds of miles from where the Japanese expected to find them. He flew missions to Balikpapan, Mindanao, even led a 4 plane raid on Palau, considered out of range of land based fighters, a base defended by 200 enemy fighters.

And from http://p-38online.com/lindy.html:
     
He flew along combat missions as an observer, and quickly calculated that the combat radius could be extended by 30%. A standard technique at the time was cruising at 2200 - 2400 rpm's in auto-rich at low manifold pressure. Lindbergh called for only 1600 rpm in an auto-lean mixture with a high manifold pressure. This reduced fuel consumption to 70 gallons per hour, and resulted in a cruising speed of 185 mph. By comparison, in July 1944, P-38s would fly a five-hour mission and come back on fumes, but after taking Lindbergh's advice, Colonel Jack Jenkins landed with over 160 gallons of fuel.