Spitfire Boost limit control

[flash2]

I see there is a boost limiter knob adjacent to the boost dial on the Spitfire and am having a boost meter made up with this limit operating off the Spitfire Boost limit Lvars . I have not seen the use of this control discussed anywhere in the Spitfire manual. Could you please provide details.

Thanks,
John

[Jacques]

Hi John,

I’m pretty sure that is a moveable bug for reference after you’ve determined your desired boost limit. Much easier to see the bug then peering at the gauge and needle, especially when it is vibrating heavily.


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[Killratio]

The "knob" is actually a screw catch which the instrument fitter tightens once the Boost Limit ring is turned to the correct value for the aircraft/engine. It isn't moveable in flight and shouldn't really ever need to be moved. Sometimes it was set at the cruising mixture/revs Boost (Weak Mixture Maximum), more often at the maximum all out level flight boost.

[Jacques]

Thanks for the clarification Darryl. I don’t think I would have ever found a reference for that anywhere in my usual haunts for specific aircraft information! I really appreciate the clarification.


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[Killratio]

No worries Jacques, it helps to have an original

[flash2]

Thank you also Darryl,

I have my new boost gauge and it is working fine but that limit function isn't working yet and I think I might have downloaded incorrectly as the gauge supplier said that specific Lvar bug is connected.

He did provide engine temperature an rpm gauges identical to those in both the T-6 and Spitfires as well as Manifold pressure for the T-6.

I will put up Gauge pictures and source contact info when I get everything together.

Thanks,
John

[Killratio]

John,

Are you perhaps confusing the Automatic Boost Cut Out Overide with the "knob" on the boost gauge?

THAT control is the red finger lever on the front of the thottle and has no connection at all to the gauge itself? in that case The gauge does not have any role at all in its operation?

Regards

Darryl

[flash2]

Darryl,

I am speaking of controlling the red sector on the periphery of the boost gauge with the gauge knob and think that I understand it's use from your previous note that it does not control anything but is a visual guide to what boost pressure to use as a function of the type of flying anticipated. My understanding is that this Red indicator is connected to the Lvar Bug for control as my gauge is operating properly. Gauge supplier says the bug Lvar is connected so I can only guess that I got an improper download or integration with SPAD.neXt.

I do see the red override in the proximity of the Throttle Lever and have not had a need used it to date.

Thanks
John

[Killratio]

That's right John, the "bug" is purely a visual guide. To be honest, even though I advised on the Spit and have been beta testing her for 8 years, I didn't even realise it was controllable!!

[Jacques]

Darryl, That is solely because you never expected it to move, so why try to make it move!!


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