Revised Bomber Power Settings

[RTHolmes]

Well it keeps on coming up so its maybe time to have a look at the power settings for heavy bombers.

A couple of comments first.
I have no beef with any of the bombers, or the guys who like to fly them. I'm not trying to make it  easier/harder to kill or survive in buffs. I believe that most AH players have an interest in WWII  aircraft which extends to the tactics used to deploy them, and would like to recreate in our cartoon  AH world the kind of realistic encounters which we've all read from pilot reports, seen in movies and  imagined ourselves. I also believe that the more realistic the modelling, the more useful real-life  tactics become. In short, the more realistic the model, the more realistic the encounters.

AH power settings model
Pretty simple (but effective) - we have a range of RPM/MP settings which can be used continuously  known as Military Power. In addition for some aircraft, we have a limited-duration  higher-power setting known as WEP. We also have settings for Normal Power and Max  Cruise, although these are suggestions rather than limits.

There is an obvious limitation with this model - there is only one option for a limited-duration  power setting, in contrast with real aircraft engines which may have several different power/duration  options. Most of the Allied aircraft I've looked at have a 5 min Takeoff/Emergency limit and a lower  1 hour Climb limit. Since the vast majority of sorties flown in AH will be under 1 hour duration, it  seems reasonable to make our WEP the 5 min limit and leave the 1 hour limit as Military  Power. Other aircraft are not so obvious - eg. the JU-88 had a 1 min setting for Takeoff, and a  30 min limit for Climb.

What I would like to see revised is the situation where an aircraft in AH can fly for an hour using settings which were only available for 5 mins in real life.

Lancaster III	RPM	MP	limit		RPM	MP	limit
Pilot Notes (Merlin 28/38)
Takeoff & Combat	3000	14-16lb	5 min
Max Climb	2850	9lb	1 hour
Max Cont Rich	2650	7lb	-
Max Cont Lean	2650	4lb	-
AHII (with suggested changes)
WEP	-	-	-		3000	14lb	5 min
Military	2850	9lb	-		2850	9lb	-
Normal	2650	4lb	-		2650	4lb	-
Max  Cruise	2300	2lb	-		2300	2lb	-

Comments
Military matches Max Climb, which is good, however the Lanc should get WEP settings as above.

B-24J	RPM	MP	limit		RPM	MP	limit
Pilot Notes (R-1830-43)
Takeoff & Military	2700	48.5"	5 min
Normal Power	2550	46"	1 hour
Max Cruise Rich	2325	35.5"	-
Max Cruise Lean	2200	32"	-
AHII (with suggested changes)
WEP	-	-	-		2700	48.5"	5 min
Military	2700	48.5"	-		2550	46"	-
Normal	2550	46"	-		2325	35.5"	-
Max  Cruise	2325	35.5"	-		2200	32"	-

Comments
All wrong here, B-24J needs completely revised settings, as above.


I realise this could get out of hand very quickly, so lets just keep the discussion to these 2 buffs to start with.

*ducks*

[Stoney]

The B-24's  "Normal" setting was not limited to 1 hour in real life.  It was labled as "continuous operation" on the engine chart, meaning you could operate the engine at that setting until you ran out of gas 4 hours later, for example.

[RTHolmes]

the spitfire's WEP, for example, was not limited to 5 mins in real life either. there are numerous examples of it being used for considerably longer than 5 mins (40mins in one example without any engine damage iirc). The figures I have used all come from official documents, and are the safe, tested and certified limits "by the book."

The B-24 chart clearly states a 1 hour limit for "Normal Power" at 2550/46". This from the now declassified Consolidated B24 Pilot's Flight Operating Instructions, USAAF and Consolidated Aircraft, 1942. I you have a better source, I'll be happy to reconsider.

In AH, however, its reasonable to use the 1 hour limited setting for Military Power. For the B24 this hasnt been done, our Military Power is actually the 5 min limited power setting, which I'm suggesting should be our WEP setting for the B24.

[Stoney]

The only operating limitation I see on the continuous operation setting is for limiting cylinder head temperatures of 260 degrees celsius to one hour.  232 degrees is the limitation for "maximum continuous".  It does not say that the rpm/manifold pressure setting itself is limited.

Perhaps you can scan and post your resource.

[RTHolmes]

http://books.google.co.uk/books?id=hu1F9PTWG28C&pg=PA122&dq=liberator+pilot+notes&lr=#PPA126,M1

I dont have a problem with the 1 hour setting being unlimited in AH, I do have a problem with the 5 min setting being unlimited though.

[Stoney]

http://books.google.co.uk/books?id=hu1F9PTWG28C&pg=PA122&dq=liberator+pilot+notes&lr=#PPA126,M1

I dont have a problem with the 1 hour setting being unlimited in AH, I do have a problem with the 5 min setting being unlimited though.

p. 47 of the same document doesn't show the maximum continuous, 1 hour limitation, oddly.

Ok, so what happens when there are planes that have a 5 minute limitation for WEP and a 5 minute limitation for Military Power?

[RTHolmes]

Interestingly the manual states that under normal conditions, climb should be at 75% of normal rated power (about 750hp at 2230/34" p.46). The shorter distances in AH and hence the need to climb as fast as possible justify using 100% (about 1000hp at 2550/46"). Contrast this with our current Military setting (1200hp at 2700/48.5").

Even with my suggested revised settings, our B-24s will be climbing at 33% more power than was commonly used in WWII. And thats just for climbing, the manual suggests a max of 735hp for level flight. My revised settings will give 1000hp, we currently have 1200hp - almost double the power commonly used for level flight. Hence the totally unrealistic speeds attained in AH and the consequent issues with closure rate etc. Although my revised settings look like a massive porking of the B-24, they only go a small way to correcting the performance.

For aircraft where there are multiple limited power settings we have to make a reasonable compromise taking into account the limitation of the AH WEP model mentioned in the OP. For your example, 5 mins at the higher setting might be reasonable for our WEP setting. For the JU-88 mentioned above I would discard the 1 min setting (our runways are long enough for fully laden takeoff not to be a problem) and have the 30 min setting as our WEP setting. I suspect this approach would be very helpful for BoB events in the absence of He-111s and Do-17s, but we'll leave the 88s for later ...

[RTHolmes]

Just to give an idea of how this effects level speed, tested @20k airstart, 50%, 20x100lb.

USAAF Setting	RPM	MP	TAS @20k
Takeoff/Military	2700	48.5"	298	current AH max continuous
Normal Rated	2550	46"	290	revised AH max continuous
Max Cruise Rich	2325	35.5"	255	max used IRL for level flight
Max Cruise Lean	2200	32"	218	typical IRL for level flight

at 20k real B-24s would typically have been making 220-250mph on their bomb run, in AH we do the same at closer to 290mph. Thats a huge difference. my suggested settings would only drop this to 280ish, but a step in the right direction.

Consider a 190-A8, at 20k about 380mph. RL level closure rate about 145mph, current AH closure rate about 80mph, revised 90mph. Thats a big difference. And this at the 190's best alt, the effect of the excess power settings gets worse the higher you go.

[Stoney]

Consider a 190-A8, at 20k about 380mph. RL level closure rate about 145mph, current AH closure rate about 80mph, revised 90mph. Thats a big difference. And this at the 190's best alt, the effect of the excess power settings gets worse the higher you go.

But the 190 wouldn't be able to run flat out either, since you'd nerf its power settings the same way you'd nerf the bomber settings, right?

[Karnak]

But the 190 wouldn't be able to run flat out either, since you'd nerf its power settings the same way you'd nerf the bomber settings, right?

Fighters ran at full power settings a lot more than bombers did.  At least that seems to be the case from all the first hand accounts I have read.

[Stoney]

Fighters ran at full power settings a lot more than bombers did.  At least that seems to be the case from all the first hand accounts I have read.

Well, why?  Same engines.  Same placarded power limitations.  If a P-47 had a military power limit of 5 minutes, but in combat they ran it at that setting for 30 minutes, what do we do in-game to accomodate the discrepancy?  Either fighters get treated the same as the bombers or vice versa.

[RTHolmes]

agreed, thats what I'm getting at - fighters and bombers should get to play by the same rules. A quick glance at the R-2800 charts shows that, as for the B-24, the P-47 in AH gets unlimited use of power settings which IRL were limited to 5 mins maximum.

From this quick snapshot of the specs, it seems that RAF aircraft are limited to the certified numbers (and even denied certified WEP settings in the case of the Lanc) whereas US aircraft get to use whatever maximum settings were anecdotally used. Perhaps someone with some knowledge of Luftwaffe specs could comment on their modelling in AH. It seems that the "Hollywood" version of WWII extends as far as AH.

[Krusty]

Currently fighters play a lot better at the rules than bombers.

Stoney keeps calling this one up, and it's apples and oranges.

Fighters were designed with speed, manuverability, and yes later they were designed expressly to shoot down heavy bombers.

Bombers were not designed for speed, or manuverability. They had 2 aspects: range and bombload. Across all other level bombers these are the 2 most important aspects that keep popping up.

190A8s, for example, are currently limited to what the placards state. No, fighters and bombers did not have the same engines, when you take into account the entire engine system (fuel, cooling, coolant, prop, running speeds). Bombers have 2x the horsepower in level flight they ever could.

So let's not bring the fighters into the equation. You don't need to. Just look at the bombers. They're off. They need fixing. Question is how and where. This is a step in the right direction, even if only limiting speeds a small percentage. What we need is to have MAP/RPM limitations tied into the AoA. So that on climb they are limited as RTholmes described.

Correct me if I'm wrong, but this CAN be modeled in AH, right? I seem to recall at least one other plane has the RPM or MAP drop during climb, but as soon as you level it goes back to normal (having to do with limited air into the engine at higher AoA).

[Clone155]

WOWOWOWOWOWOWOW! I just got a really good idea!!! (bear with me on this one..)

You know how in the MAs the fuel is set low right? for example... the typhoon gets about 23 minutes of fuel with 100% going military power, now what if CHANGED IT so that 23 minutes of fuel is NORMAL POWER? I think this would force people to fly normal power like they do now with military power, and military power would be like WEP. Well that was my big Idea, what do you think?

[Messiah]

WOWOWOWOWOWOWOW! I just got a really good idea!!! (bear with me on this one..)

You know how in the MAs the fuel is set low right? for example... the typhoon gets about 23 minutes of fuel with 100% going military power, now what if CHANGED IT so that 23 minutes of fuel is NORMAL POWER? I think this would force people to fly normal power like they do now with military power, and military power would be like WEP. Well that was my big Idea, what do you think?

Terrible.