How to stop OVERSPEED OF ENGINE

wm708 · #1 08-15-2016, 10:51 PM

I BELIEVE SOME OF THE ELECTRONIC IGNITIONS HAVE SPEED LIMITERS ON THEM.
As Magneto's do not have this feature. And you have a governor failure this might help stop a overspeed.
Maybe some of the electronic ignition vendors can chime in on this part .
Drag cars have had this feature for many years.
Bill J

KRviator · #2 08-16-2016, 01:19 AM

Disabling the ignition automatically will not stop an engine overspeed caused by a governor failure driving the prop towards fine pitch.

The reason it works in a car is the engine is driving the vehicle independent of the gearing. IF you were to jam it into first gear at highway speeds then pop the clutch (simulating a governor failure in a plane), you'll overspeed your engine irrespective of your non-firing spark plugs.

rv6ejguy · #3 08-16-2016, 05:53 AM

Quote:

Originally Posted by wm708

I BELIEVE SOME OF THE ELECTRONIC IGNITIONS HAVE SPEED LIMITERS ON THEM.
As Magneto's do not have this feature. And you have a governor failure this might help stop a overspeed.
Maybe some of the electronic ignition vendors can chime in on this part .
Drag cars have had this feature for many years.
Bill J

Our CPI and EM-5 both have rev limiter functions. Could save you a heap of money in the event of a prop governor failure.

BillL · #4 08-16-2016, 06:33 AM

Quote:

Originally Posted by rv6ejguy

Our CPI and EM-5 both have rev limiter functions. Could save you a heap of money in the event of a prop governor failure.

Yet another good reason for these products!

Walt · #5 08-16-2016, 06:47 AM

Adjusting the low pitch stop on your prop will prevent an overspeed, this should be done as part of your initial setup of pitch stop/governor setup.

Edit: this will require more investigation, although it may help it may not prevent in overspeed in cruise.

Lenny Iszak · #6 08-16-2016, 06:56 AM

Quote:

Originally Posted by BillL

Yet another good reason for these products!

If you have two of those yeah, but if you still kept a mag, that will keep feeding the revs.

Aren't the pitch stops on the prop supposed to stop it from overspeeding?

rv6ejguy · #7 08-16-2016, 07:01 AM

It should be stated that electronic rev limiters will not save ALL overspeed events but will be helpful in a vast majority of cases outside of "downhill" flight events.

If your prop goes full fine at high power in cruise or with the nose down without a rev limiter, adjusting the pitch stops won't do much for you I don't think. The prop is unloaded considerably in flight compared to static so is never close to the low pitch stop in flight except at low power settings and low speeds like on approach.

ronschreck · #8 08-16-2016, 07:26 AM

Quote:

Originally Posted by KRviator

Disabling the ignition automatically will not stop an engine overspeed caused by a governor failure driving the prop towards fine pitch.

The reason it works in a car is the engine is driving the vehicle independent of the gearing. IF you were to jam it into first gear at highway speeds then pop the clutch (simulating a governor failure in a plane), you'll overspeed your engine irrespective of your non-firing spark plugs.

Well, not always. In an enroute climb, where the engine is supplying power to the propeller, an overspeed may be avoided if power is immediately shut down by an RPM limiter following a governor failure or loss of oil pressure to the prop hub. A limiter would be useless in cases where a low pitch propeller could drive the engine such as during a high speed descent.

Weasel · #9 08-16-2016, 08:00 AM

[quote=Walt;1103643]Adjusting the low pitch stop on your prop will prevent an overspeed QUOTE]

Are you sure about this? With the low pitch stops set per manufacture for proper take-off RPM at rotation speed and then flying at over 175 knots TAS in a less dense air mass I don't see how the low speed stop can prevent overspeed. There is quite a bit of blade pitch angle difference.

Walt · #10 08-16-2016, 08:16 AM

[quote=Weasel;1103660]

Quote:

Originally Posted by Walt

Adjusting the low pitch stop on your prop will prevent an overspeed QUOTE]

Are you sure about this? With the low pitch stops set per manufacture for proper take-off RPM at rotation speed and then flying at over 175 knots TAS in a less dense air mass I don't see how the low speed stop can prevent overspeed. There is quite a bit of blade pitch angle difference.

Hmmm, you have a good point, no I'm not sure and will need to look into this more now.