Hawk81A-2
 

Would be curious to know differences in game between Hawk81A-2 and P40B. Perusing my sources (Jane's and "P-40 in action") can't detect any.

Thx,
GB

I believe that the Hawk81 reflects the version of the P-40B used by the AVG. There might be some minor differences in armor and armament compared to the actual USAAF P-40B, but I'm not sure. Maybe lack of self-sealing tanks?

Apparently, the really early versions of the the P-40 lacked armor and self-sealing fuel tanks, and just had 4 guns. They were used by the DAF under the name of Tomahawk Mk I.

Ah, this thread has the goods. The AVG Hawk-81s were ex-RAF with British .303 MG instead of US .30 or .50 caliber, plus an up-rated engine.

http://www.ww2aircraft.net/forum/avi...2-a-23934.html

Sorry, I was unclear.

I meant I would know difference between the two types in game. In reality it seems officially there weren't, but I read at least a former AVG pilot's report that stated differences of their P-40's in respect of stock ones. Since Oleg put two distinct SUCHAISVOLOCH's for Hawk81A-2 and P-40B, I wonder what changes introduced among them.

This is the link for document I previously mentioned. It is actually pilot's manual with some comments and additions. It's a 236 KB PDF, so it'll take a while to be loaded.

http://www.avia-it.com/act/profili_d...0_Tomahawk.pdf

Ah, that I don't know. I naively assumed that the Hawk-81 in the game was based on historical evidence. Perhaps a modder or a DT member who's seen the FM code for the model could tell us.

I can't tell you about the FM code, but when I originally built the H81-A2 pits (along with the P-40B/C and Tomahawk IIB/IIC pits) for PacFi, the idea was to depict the AVG's aircraft specifically.

My research indicated a few things:

- the AVG's aircraft were transitionals that didn't fit the exact technical order of any of the contemporary USAAC or RAF P-40 models.
- They arrived in Rangoon without wing guns. The AVG scrounged two squadrons worth of either .303 or .30 cal Brownings, and one squadron's worth of 7.92 guns; I believe (it's been 8 years, pardon my memory) that they arrived with the .50 cal nose guns, as Chuck Baidsen recalls working with .50 cal ammo and having to link much of it manually
- Because the aircraft, and their engines, were unusual diversions from the hectic war production lines, Curtis was short on engines to equip the aircraft. As a result, they hand-fitted rejected parts together until they had enough functioning engines. Because those engines were literally hand-fitted, the tolerances were much closer than most and the engines resultingly produced more power than production line V1710s. This is corroborated by experiences of the pilots, ground crew... and the IJA. :cool: Some reports put the resulting HP figure north of 1200, and several points in my research mentioned 50" or more of manifold pressure.
- The aircraft also arrived without proper reflex gunsights and the AVG field-fabricated their own reflectors to make due. That is what led to the unique hanging sight in the H81-A2 pit model, and it was modeled based off photos of the actual AVG sights (which were VERY hard to come by, especially in 2004!)
- My photographs did NOT show angled cockpit armor glass like the plate in the Flying Heritage Collection's restored P-40C.
- There were conflicting reports about the AVG aircraft's capabilities to carry bombs (there were some field experiments to try and add that option, but the "how" is lost to history), but all my sources concluded they could NOT carry drop tanks.
- They also lacked the self-sealing fuel tanks of P-40Cs
- They featured earlier control-stick mounted hydraulic actuator switches, which I missed when I built them.
- Dan Ford's research, and Erik Shilling's notes, indicate they had earlier foot treadle starters. I couldn't, and still can't, find a photograph or diagram or anything except brief mentions of this system, versus the later toggle switch starter. That feature, though, indicates the aircraft significantly preceded the P-40C production span, as it was eliminated early in the H81 model line.
- The FM (hopefully) also reflects the droop (less than an inch) that was added by the AVG to the ailerons which benefited handling.

Really interesting information Plane Eater. Glad to have you and your knowledge around!

Late in replying!

Plane-Eater has done his homework for sure. In my own research I have found the same things he did.

I can add a couple details though, which don't really trasnlate into in-game performance

Curtiss cheated on a lot of the original RAF order according to what I found. They used some- maybe a few, maybe more- self-sealing fuel tanks, but they were externally sealing instead of internally sealing.

Curtiss used 'close enough' paint colors instead of the RAF dictated shades. This gives rise to some confusion regarding actual AVG camo colors, especially on the belly

When painting, Curtiss used rubber mats as stencils, so the paint schemes were very very similar, plane to plane. They used 'A and B' stencils on most, resulting in the asymetrical camoflage like on Hammerd's default skin. However, some few were symetrical "A+A" schemes that had the same camo on both sides of the plane.

To touch on Plane-Eater's comments on the engines, AVG Hawks had certain, common failures on 'stock' components that suggest strongly that the AVG powerplants produced more power than a 'standard' H81 engine

Something I've never seen on a skin yet- the AVG H81s in Burma, particularly in the Rangoon area, developed a green mold in the cockpits quickly. I was tempted in my skins to show this, but then I'd have to make dupes that didn't have the green crud, and you wouldn't see it in the in-cockpit view anyway, so I nixed it

The V1710-33 as used on the H81's had no automatic boost regulation. This means it essentially was up to the pilot to control the boost, up to full throttle at nearly all altitudes. It was therefore extremely easy to totally overboost the engine when flying at low altitude and getting a lot of extra power out of it. This, of course, would cause mechanical failures of all sorts rather quickly.

That's not what I mean at all. I don't mean that common failures were encountered. I mean that specific things happened which were common to the planes the AVG had, that suggest this is the case.

I'm not really going to argue about it; this isn't my opinion formed aver an hour or two online. This is what I turned up over years of looking at reference. As such, I term it a thing that "suggests" strongly that this was the case.

Regarding that engine, well the biggest one entrusted to me was a Lycoming opposed 6 so a big Alison was definitely never under my wrench, and I don't know every nuance of their operation. But I do know that the records we can research are kind of muddled on these aircraft and all their equipment.

For example, Curtiss wasn't even sure what precise model planes went to Rangoon. H81A-2? H81-A2? H81A-3? H81-3A? Depending on the source, different designations may be found referenced. Maybe typos at Curtiss? Nobody knows. Alison thought the engines were V 1710 C 15s, according to a letter from an Alsion rep in Rangoon in Sept. 1941. Curtiss thought the planes were equivalent to Tomahawk MKIs. The equipment suggests the MKII variant instead. But some had equipment that suggests neither specific model. The pilot's manuals' info is slightly suspect because the manuals may not have actually been for those precise model planes.

And on it goes

If the AVG did use higher boosts systematically, then they'd have both higher power output and more engine failures, no matter if the engines were hand crafted or standard production line.

What 'certain, common failures on stock components' did you find they encountered?
How do you think they created the extra power output you mention?

Just to be clear - I mean no disrespect or anything, and do not intend to argue. I'm just curious. Personally, I see a connection between high boosts, high power and high failure rates, but if there's something on top of it and more specific to the AVG, I'm more than willing to learn about it.

I think I already mentioned I didn't come here to argue with you. I post here quite rarely and I'm sorry I decided to participate this time, too

It's of course up to you to decide not to share what you know, shame though. Does anyone else have an idea what 'specific things happened' and which 'certain, common failures on 'stock' components' occurred, and maybe also how this is related to a higher power output but not to the higher boosts used?

The AVG P40s had a very high failure rate of the prop reduction gear boxes.

Guys, I have worked with both of you on Curtiss related things. FormerOlder has done an exhaustive amount of research on the AVG over the years, and JtD is also well versed on things Hawk, I see no need for you guys to have a spat.

Even without the manual boost control issue, the hand fitted Allisons that were installed on the AVG Hawks did indeed produce more power than standard issue engines. This alone could be the cause of the high failure rates of reduction gears.

Just saying it's because of manual boost controls plays too much into the revisionist view that the AVG's pilots were inferior. Their combat record in the short time they flew stands in very stark contrast indeed to the modern, and wrong, thinking about them.

Thanks for the information. I still don't really get why the extra power is not supposed to be related to application of higher boost, in particular where Plane-Eater says he found that mentioned. If you built two alike engines just with different tolerances, the high quality version might be somewhat more powerful due to higher efficiencies (less losses), but that's not going to be excessive unless the standard production quality is abysmal. You'll need to increase boost or rpm in order to get more power out of it.

Regarding manual boost control means inferior pilots, imo that's not the case at all. I think looking at the record of the AVG and the conditions they operated under speaks for itself. Manual boost control means that it is simply a matter of clearance and application of boost levels in the field, suited to the conditions on site, with no technical changes to the engine or aircraft. With the P-40, this was done, too, with several squadrons considerably exceeding official limits. The point here is that higher quality engines should have less trouble with overboosting than standard versions might have, as they would most certainly be more reliable.

The application of 50" boost would yield an increase of about 340 hp (35%) at low altitudes over the standard emergency power settings. You'll get nowhere near this with just manufacturing (reasonably) higher quality.

Afaik, flight model wise there's no difference in game between a P-40B and the AVG Hawk 81. If I look at this topic, I think it would be better if there was a difference. But there's not much hard evidence to allow modeling a deviation from official specs.

Former_Older and JtD,

Check your PMs.

:cool:

JtD:

Sorry to dig out an old thread. From a quick search in a few places online I vaguely remembered, the AVG had repeated issues early on with thrust bearing failures in their engines. I think it was Molesworth's Sharks Over China as well as Clemmon's book on the AVG that mentioned a field-modified oil recovery and sprayer system was devised to sump extra oil and deliver it back onto the bearing.

That kind of failure in the reduction gear case, from my understanding, is a symptom of higher power loads over a significant period of time than the reduction gears are rated for. I'm not an engine expert, though, so somebody who knows the old war engines better than me might be able to elaborate.

The AVG-vintage pilot manual on Dan Ford's site mentions 41" Hg as max boost at sea level. I've seen a multitude of sources, including my brief contact with Mr. Shilling before he passed, that indicated 41" was... we'll call it highly conservative. 41" was routinely exceeded by a notable margin.

Dan Ford has updated some of his research since I was last involved heavily, and his work is extensive and exhaustive. I'll need to brush up before I try to speak authoritatively on too many more specifics. : )

EDIT: Like I mentioned above, I'm not an engine expert, but wouldn't closer tolerances also allow (at least to some extent) higher loads than the design rating without the same level of wear or failure? IE, you could run the engine at - for example - 115% rated output without as much / as many of the corresponding wear and problems that would cause on a stock engine? So along those lines, by the time you did finally start getting high-load related failures, you'd be running at WAY more than just 5 or 10% above max rated output?

You would have to check the standards of the engine makers in those times. I don't think that P&W held Rolls Royce tolerances, FWIW. Maybe see how they compared to Detroit automotive. A whole lot depends on how many and which parts they hand-matched.

The difference can be a stock engine vs a "blueprinted" engine.

Not necessarily so, closer tolerances can contribute to less power loss and less variance in parts failure. For instance, if you achieve the same compression in all cylinders with zero tolerance, tolerance will see some cylinders with higher than normal and some with lower than normal compression. Operationally, you'll have to run the engine at a boost level which is save for the cylinder with the highest compression, so it is save to increase boost level when you have no tolerance at all. However, you can increase the boost level so that with zero tolerance all cylinders fail, while you'd still have some cylinders running on the engine with tolerances.
For prop reduction gear I don't know the effects of tolerances, but frankly there's little I can think of to turn a rejected part into a superior one. That might be a reason they were the weakest link.