General information about Wing42's Lockheed Vega.
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Joined: 17 Jul 2017, 15:19
Location: Görlitz, Germany


Post by Vitus » 22 Jul 2018, 18:43

Hello Tom and Jarek,

I keep reading over the conversations by pm we had and I can't really figure out what the conclusion is in regards to the "supercharger"/"b"-lever discussion, so I thought maybe you could help me with this question.

It boils down to this:
1. was I right in my initial assumption that the supercharger could be engaged/disengaged with the "b" lever of the throttle quadrant?
2. How much of an impact would the SC1 supercharger really have?
3. Is the procedure for the supercharger, as described in the checklist correct from your estimation? I.e. disengage during startup and engage it once the engine is running?

I'd appreciate your input. 8-)
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Re: Supercharger

Post by Jarek » 22 Jul 2018, 20:07

Hello Otmar,

The conclusion is that this is mixture heater, as documented in the Wasp SC1 manual from 1929. This is the only reliable source of information that we have today. So this is part of fuel system model - with hazard of carburetor freeze and loss of power if mixture is above 10 degrees. This is quite challenging to keep it in recommended range (4-10degC) as we have no gauge to monitor this yet in this plane. I believe recommendation was to do it by ear, but this requires good sounds which are not present today. So only some math model could be considered for now.

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Re: Supercharger

Post by Tailspin45 » 17 Oct 2018, 16:06

For the record, I still don't have an answer to the "B" knob question. I've talked or corresponded with people at four museums and three P&W engine shops. They all indicate that the early 1340s had a blower clutch, but it was internal with no manual control. The small Wrights didn't have a supercharger, and the larger ones had a clutch, but it was also internal. I've searched high and low for 1920-30 vintage parts catalogs, without success, hoping they would shed some light on the issue. I have recently joined the American Aircraft Historical Society so I can rummage through their back issues, and I will join the Experimental Aircraft Association today so I can access their Vintage forum. Meanwhile, I've found over 400 pages of original Lockheed material that has to be copied and mailed so it will be at least a couple weeks before we can see what's what there.

As for the mixture heater, the Wasp had a so-called hot spot heater which had no controls that I can other words, it was different from carb heat.

Most old aircraft didn't have a carb temp gauge, and the procedure was to turn the carb heat on full if you suspected a problem and always during reduced power such as landing. I came very close to landing on a highway after picking up a load of carb ice in a Cub. That particular airplane made ice faster than a refrigerator! There was no indication until suddenly the engine started running very rough. And, of course, when you turn the carb heat on it makes the air less dense and the mixture richer still so upon application the rough running gets worse, in some cases for 30 seconds or more. You think when dealing with ice you wouldn't sweat, but a rough engine crossing a mountain pass will make you sweat.

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