Friction Lock on Throttle Quadrant

[Charles Davis]

I'm going to make my own throttle quadrant (just having fun).

I was wondering everyone's opinion on the following:
1. Is a in-flight adjustable friction lock desirable?
2. Is a stop to prevent the mixture being closed accidentally desirable?  I'd have a simple spring loaded plunger you'd have to pull to allow the mixture to be closed the last 1/4 travel.

Thanks.  I want to keep things simple and light, but also want these features if they are useful in the real world.

[Waiter]

1) Nah. There needs to be a way to adjust it, but once its adjusted, you probably won't touch it for a couple years.

2) Nah


Waiter

[dave]

friction lock is an Aviation Standard...and keep it KISS,ed up..  you wont regret it.

[Charles Davis]

Dave,

AWESOME LEAD!  EXACTLY what I was looking for!    

[Drew]

Inflight adjustable friction lock is not required----however, you will need to adjust the friction.  If the friction is not high enough, the throttle will creep and drive you nuts.  The bolt that holds the throttle in place is what adjusts the friction.  Start light on the friction and adjust until the throttles no longer creep----then you never need to adjust.

[Matt]

I don't think a mixture block is going to work very well.  In
my experience with aircraft engines, there is too much variability
in the appropriate mixture setting depending on power setting,
temperature and altitude.  I think that's the point of having a
mixture control to start with..  The aircraft carburetor is almost
completely un-compensating.  The correct idle setting on the
ground at Alamosa CO on a hot day would be way too lean for
the engine to even run on a cold day in Seattle.  If the goal is to
keep from accidently killing the engine, where are you going
to put the stop but still allow enough leaning when its hot and
high?   If you figure it out, let me know - I have accidentally
killed my O-200 while taxiing.  Especially annoying because I
don't have a starter.  Matt-

[Charles Davis]

Matt,

I was thinking of putting a latch that would prevent the mixture from being retarded below 25%.

The idea is to prevent the mixture from accidentally being retarded so far as to make the engine stop.

[Matt]

I think there are times when you need to be able to set the mixture
more lean than 25% to have it set properly.  Sorry I used so many
words to say this in my last message..

Matt-

[Charles Davis]

The stop would be a simple spring loaded tab.  As you pull back on the mixture, your thumb is used to move the tab, allowing the mixture to retard below 25%.

So, you could retard below 25%, but it would have to be a conscious act.

The thing I'm trying to prevent is accidentally retarding the mixture.  

The big question is, am I trying to "solve" a problem that doesn't exist?   Has anyone ever accidentally pulled back the mixture and shut down the engine (say, when pulling back power when entering the pattern).

[Dan Patch]

I'd vote with the other posters on this topic - 1) You will definitely need some sort of adjustable friction to prevent creep during flight, but you will find little to no need for in-flight adjustment.  I set the friction on my Brock throttle quadrant almost 24 years ago and haven't needed to touch it since!  2) I wouldn't recommend restricting the ability to lean.  Even on the ground at sea level I find that I can lean very agressively at idle, keeping the plugs and prop clean.  

In terms of bumping the mixture in the air, it has been my experience that with the Brock/Rutan setup you are far more likely to nudge it rich in the process of thrashing around dealing with charts, reaching into the back for something, etc.  While this seems benign, the problem is that you can potentially run for quite a while very rich, which can screw up your range if you aren't paying attention.  I find my fuel flow gauge invaluable for this purpose alone (i.e., detecting abnormal fuel flow rates).  Failing to lean or lean properly (or stay leaned?) has brought down at least one EZ short of an airport (probably a lot more than one).  (Haven't been there or done that, thank goodness!)  

If you go too lean in the air the prop stops, your heart stops, you push the mixture rich(er), the prop starts immediately and your heart eventually restarts.  If you go too rich, when the prop stops you may still be short of the tie-downs... and it isn't going to restart (of course in a VariEze, you select the reserve tank and on keep truck'in, but we're not counting on that, right?).  After flying with fuel flow instrumentation for a number of years I would very strongly recommend having it in the panel, it's one of my PRIMARY engine management instruments and I'd be very uncomfortable flying without it.  

Blue skies,

[Dan Patch]

The big question is, am I trying to "solve" a problem that doesn't exist? Has anyone ever accidentally pulled back the mixture and shut down the engine (say, when pulling back power when entering the pattern)....

Oops, I guess I didn't really directly answer your question.  I've never accidently shut the engine down in the air with the mixture.  I have pulled it lean on the ground a few times as the result of TWKS (Transient Wrong Knob Stupidity), but not to a full flame out (amazing how fast you can undo a boo-boo when the engine tries to go silent!).  Once every year or two I've bumped it rich for 1 to ~10 minutes before catching the problem.  

I'd encourage caution in solving hypothetical problems because the solutions are NOT hypothetical and can introduce unanticipated REAL problems.  Asking questions to sort out those that actually occur before launching into a "fix" is the right approach - keep it up!