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  • Please see the most recent updates in the "Where did the .com name go?" thread. Posts number 16 and 17.

    Post 16 Update

    Post 17 Warning

B-17F

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I'm reading a book called “North Atlantic Cat”, by Don McVicar. Actually I'm re-reading it, but whatever. This guy flew for RAF Ferry Command, and got to fly a lot of different planes, among them the B-17. Here's what he said about his first time in a B-17F:

“It was a B-17F, FA699, which the RAF called a Fortress. It was the first I'd flown with the more highly rated Wright Cyclone GR-1820-97 engine with a 'War Emergency' power rating of 1,380 horsepower. It featured General Electric turbo-superchargers which meant you took full throttle most of the time and used a single bakelite dial to select the boost you needed.”

What?? I know what “boost” is, what our friends across the ocean call manifold pressure. But what's with this “always flying around at full throttle and select the 'boost' you need with a bakelite dial”? I've never heard of such a thing.

- Paul
 
No not the bakelite. I know what that is too. What I meant was, I've never heard of placing the throttles at full power, leaving them there, and then adjusting power by some "other" means, by some "dial" apparently related to the superchargers. What dial? I've never heard of this before.

- Paul
 
Is this the reference do you think?

There were two types of control systems for the turbosuperchargers: oil and electronic. The oil-controlled models had levers in the cockpit
that would individually set the turbo boost for each engine, and these levers had to be set manually by the aircrew to provide the
appropriate level of boost. The electronic control, known as the Pressuretrol system, had a single large knob incremented from 0-10, just
like the volume level knob on a common home stereo system or car radio.

best

nio
 
That sounds like what McVicar described. So is that correct, you set the throttles to full and just leave them there until you land? He did say they were at full power "most" of the time, not "all" of the time. So when are they not in full power?

- Paul
 
Not so sure he was using corect procedure, but the control he was using controlled the turbocharger wastegate. By opening and closing the wastegate one controled the boost. As a kid i remember a lot of wwii era stuff around was made of bakelite, especially popular were knobs, jacks, small stuff now often in some plastic or another. Probably an electric controller. There is enough flow resistance in such a system that to, climb and cruise power would mostly depend on some sort of boost asistance and could be controlled just by the turbo. Because of the requirements to vary power more quickly and tactical and single pilot operation fighters used a more automated system.

I have not researched the vagaries of the particular system here, but I expect more sophisticated systems inhabited later models.

Cheers. T
 
Yes guys,

for normal flight the throttles will be full forward and the dial will be the main control you use for control. Its why the B-17 (later models) is nearly as easy to fly as a piper cub.

thanks,
Lewis
 
Late B-17F's and B-17G's used that setup, where as earlier F-models and all earlier B-17 makes (with turbo-superchargers) had four independant turbo-supercharger boost levers in that location. I believe B-24's/PB4Y's followed the same route, with early/mid variants having the four independant turbo-supercharger levers, and later switching to the single "MP Selector" dial - all to help make the pilot's duties a bit less complex.
 
Great link Tom, thanks!

What an amazing system. I wish I knew of it when I took my ride in "Liberty Bell" a couple years ago. I could have watched them use it. I'll bet that big knob is a detent type selector, you know a "click-ckick-click", type knob, rather than a smoothly rotating one. Otherwise you could accidently brush against it and change power setting while reaching for the coffee cup...

- Paul
 
Exactly, when Scott first explained the system to me as an example of how easy to fly the bird can be when you have a crew it instantly became my favorite 'lazy' cruiser.
 
I wonder if the Liberty Bell still has its turbos. Most warbirds remove them due to maintance issues. I do know one Liberator making the circuits does still have them as they had pieces of #4 system strewn across the ramp chasing down some gremlin.
 
Also a nomenclature thing. Large piston engines have a couple of 'full power' settings. He is likely in 'max continuous' or 'max cruise', being the maximum MAP and RPM for a given altitude that you can run at continuously without having to navigate home by the oil slick and debris trail. There is 'Max economical' cruise settings- slower, burning less go juice. Takeoff -which may be 'wet' or 'Dry' settings if equipped with ADI or not- 50-50% methanol-water mix injected to prevent detonation at high MAP, allowing some of the big mills to push 60 ''Hg- for very short periods of time- typically untill you get airborne and cleaned up for climb, and a some what lower '5 minute rating' or METO-'Maximum Except Takeoff' -more than 5 minutes and things start overheating and causing increased wear or damage. Military users will often have a 'War emergency' rating, again; for short periods of time, all or nothing to get your butt out of the crack before your engine gives up and leaves you to deal with a bunch of agitated folks you just did you level best to kill; though some mills-the R-2800, 'fur instance, are renowned for being able to exceed max ratings for insanely long periods. Ira Kepford famously; in the course of out running a whole gaggle of irate Nipponese Naval Aviators, ran his Corsair at War Emergency untill the Zeros ran out of ammo and gas. Even more amazing, his enigine had a couple of jugs with 'ears'-rocker boxes-shot away, holes in cylinder walls and crankcase, his aircraft thoroughly perforated, and he was short a thumb and an ear and picked up a few other holes that were not spec for a human male.
So it all depends on the type and variant. Type training on large piston aircraft, for that reason, really hammers on engine handling.
 
Tom, as far as I am aware, all of the B-17's operating today do have the turbos installed, but none of them have the turbos actually working - they are just fixed open, with the exhaust passing through. Even though every B-17 operating today (all G-models (with one cosmetic F-conversion)) have that boost-control dial in the cockpit, it isn't used as the turbos don't function, so it is all in the throttles. Essentially those items are there just to "complete the picture". Because each engine is different, it also always caught my eye when I was younger, that each throttle lever and each prop lever are usually in slightly different positions from one another, while operating the aircraft, to get each engine to the same power setting.

Within warbirds that fly today, you can probably count on just one hand the number of them that have functioning turbo-superchargers. The only ones I can think of are the P-38L "Ruff Stuff" (the only P-38 flying today to have them functioning, and not just fixed open (though it won't be the last, judging by those under restoration right now)), and the Flying Heritage Collection P-47D (restored by Westpac) and the Westpac operated P-47D. And none of these are really for the need to have them operating, but just to make the aircraft more original. It will be curious to see if the ultra-authentic restoration of the combat-vet P-47D "Dottie Mae" will have a working turbo-supercharger as well (due to likely be complete and flying within a year or two).
 
Man I'd love to hear some warbirds with the turbos going! I've read that they contribute significantly to the sound of the plane from the ground!

- Paul
 
Regarding "Ruff Stuff", I don't know if they always have the turbos functioning, or if sometimes they may have them wired open just for everyday flying (most of the P-38's I'm aware of, don't have all of the parts to even have them functioning - for instance, despite the acclaim that "Glacier Girl" has, it actually is void of some items that would be needed to make the turbos work, but will be incorporated into another P-38F under restoration right now at Westpac (from what I recall, these left-overs from the restoration of Glacier Girl that weren't incorporated, were sent to Westpac for their use). At Oshkosh 2007, when "Ruff Stuff" debuted, they definitely did come with the turbos functioning. In this video, you can hear the "whistle" as power is applied and the fans spin up (really cool I think!): http://www.youtube.com/watch?v=d6wHblArFfA

Regarding the FHC P-47D, and the Westpac P-47D more recently, which have both been reported to have working turbo-superchargers, I haven't been able to find any takeoff videos which one could clearly say you can hear it - which may be simply due to the internal configuration or the way the system operates on the P-47 - but perhaps they do sound a little different even in standard operation than other P-47's without all of the internal functionality 'plumbed in'.
 
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