Magnetos---best way to check
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The Bulldog had (has) a rotary mag switch, which controlled both mags, rather than two separate ON/OFF switches.
I can remember one of the Standards Squadron examiners telling me that it was possible for the metal contacts in the switch itself to malfunction such that at "OFF" the mags, or at least one of them, wasn't grounded.
The mags could still be grounded separately as normal, because the switch used different contacts inside the switch body to ground them at the L/R positions.
Unless a ['Both mags OFF / "Drop & Stop"] check was done, you wouldn't know the switch contact had failed.
I can remember one of the Standards Squadron examiners telling me that it was possible for the metal contacts in the switch itself to malfunction such that at "OFF" the mags, or at least one of them, wasn't grounded.
The mags could still be grounded separately as normal, because the switch used different contacts inside the switch body to ground them at the L/R positions.
Unless a ['Both mags OFF / "Drop & Stop"] check was done, you wouldn't know the switch contact had failed.
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This "dead cut" several have mentioned presumably means they go to off with the magnetos. Fine, if you intend to let the engine come to a complete stop, and then wish to restart. However, it tells you nothing and accomplishes nothing. You already know the mags are grounding out by doing a standard mag check: both-left-both-right-both. No need to go to off. Off doesn't tell you anything that the other positions haven't already told you; the P lead is intact and grounding the mag through the switch.
This is not true. If you've ever had a rotary type mag switch apart you will know that the OFF position is internally a different terminal for the contact to 'make'. So, testing L & R is not testing the OFF position within the switch. And yes I have seen this problem and that was reason I took the switch apart. This may be the reason why the DEAD cut check appears in some check-lists.
This is not true. If you've ever had a rotary type mag switch apart you will know that the OFF position is internally a different terminal for the contact to 'make'. So, testing L & R is not testing the OFF position within the switch. And yes I have seen this problem and that was reason I took the switch apart. This may be the reason why the DEAD cut check appears in some check-lists.
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Exactly, which is why we should all obey the POH and not rely on advice given elsewhere if it contradicts.
Individual magneto switches present a different situation to a rotary, combined switch. In an aircraft fitted with individual mag switches, I would certainly agree that a dead cut check is unnecessary.
Personally I would prefer individual mag switches as I see them as a safer way of doing things.
I know of one case where one of our RAF Bulldog aircraft developed a badly rough running engine and was unable to maintain height. My colleague who was on an instructional sortie then discovered the rotary mag switch was the problem and it was intermittently grounding out the mags. Going to "L" and "R" didn't cure the fault. He was able to recover the aircraft by holding the switch in a certain position just away from the "BOTH" setting while his student flew the aircraft to the overhead where they cut their losses and flew a forced landing pattern to the grass.
Individual magneto switches present a different situation to a rotary, combined switch. In an aircraft fitted with individual mag switches, I would certainly agree that a dead cut check is unnecessary.
Personally I would prefer individual mag switches as I see them as a safer way of doing things.
I know of one case where one of our RAF Bulldog aircraft developed a badly rough running engine and was unable to maintain height. My colleague who was on an instructional sortie then discovered the rotary mag switch was the problem and it was intermittently grounding out the mags. Going to "L" and "R" didn't cure the fault. He was able to recover the aircraft by holding the switch in a certain position just away from the "BOTH" setting while his student flew the aircraft to the overhead where they cut their losses and flew a forced landing pattern to the grass.
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Individual magneto switches present a different situation to a rotary, combined switch. In an aircraft fitted with individual mag switches, I would certainly agree that a dead cut check is unnecessary.
Not necessarily true. If you take a Chipmunk as a case with individual switches although you have tested left and right it's very difficult to detect a RPM drop so all you've done is proved that both mags are working. You've haven't proved whether one mag is permanently live or not. I know I'm a pedantic old fool - sorry. But this very situation occured to my knowledge recently and the only way to eventually stop the engine was by turning the fuel off, which of course took some time. Certainly worried the pilot who thought he was never going to be able to stop the engine. No ICO you see!
Not necessarily true. If you take a Chipmunk as a case with individual switches although you have tested left and right it's very difficult to detect a RPM drop so all you've done is proved that both mags are working. You've haven't proved whether one mag is permanently live or not. I know I'm a pedantic old fool - sorry. But this very situation occured to my knowledge recently and the only way to eventually stop the engine was by turning the fuel off, which of course took some time. Certainly worried the pilot who thought he was never going to be able to stop the engine. No ICO you see!
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Doesn't matter what theory or rule is quoted - we all know that someone will beg to differ.
In that case, the dead cut check is when you switch off both mags
If you want three opinions, put two pilots together
What does the POH say?
In that case, the dead cut check is when you switch off both mags
If you want three opinions, put two pilots together
What does the POH say?
