Choke Management

[skippydiesel]

I fitted my last aircraft with a nifty motorcycle choke that had a friction nob so that I could lock it full closed, thus freeing my hands to do other things in the cockpit while I started the engine.

 

My new aircraft comes with a genuine aircraft choke, that must be held in the full closed position for starting (no friction devise). I find this to be very inconvenient. A  third or even forth hand, would be a great help. In leu of additional hands ,this is what I have come up with:

Crude, simple, efficient, cost effective and allows for half choke very soon after start 

 

[sfGnome]

Very inventive. Now you just have to find a place to clip them when not in use. It’s just occurred to me that there is a whole generation (or two?) of car drivers who would have no idea what a choke is. Damn, that makes me feel old! 🤨

[facthunter]

The choke on a Bing is not a real choke. It only works if the throttle is near closed.  Nev

[kgwilson]

Correct and the engine won't start if there is any more than a crack of throttle. Part of the cold start procedure is to make sure the throttle is fully closed. The choke stays where it is put on my Bing.

[440032]

I know a girl called Peg. (I met her on line....)

[facthunter]

A lot of Pegs hang out on line   Nev

[Thruster88]

19 hours ago, skippydiesel said:

I fitted my last aircraft with a nifty motorcycle choke that had a friction nob so that I could lock it full closed, thus freeing my hands to do other things in the cockpit while I started the engine.

 

My new aircraft comes with a genuine aircraft choke, that must be held in the full closed position for starting (no friction devise). I find this to be very inconvenient. A  third or even forth hand, would be a great help. In leu of additional hands ,this is what I have come up with:

Crude, simple, efficient, cost effective and allows for half choke very soon after start 

 

You could move the start button between the park brake valve and the choke. Fingers on the choke, thumb on the start, other hand on throttle. Problem solved. Got a pic of the entire panel layout? 

[Blueadventures]

58 minutes ago, Thruster88 said:

You could move the start button between the park brake valve and the choke. Fingers on the choke, thumb on the start, other hand on throttle. Problem solved. Got a pic of the entire panel layout? 

Agree, needs rearrangement.  Pegs stupid.  I would have had the start button and enricher (Choke) closer, from the getgo.  Moving the Alt / Battery switch unit will also allow them to be closer.

[old man emu]

22 hours ago, skippydiesel said:

Crude, simple, efficient, cost effective and allows for half choke very soon after start 

You've got that pegged!

[skippydiesel]

2 hours ago, Blueadventures said:

Agree, needs rearrangement.  Pegs stupid.  I would have had the start button and enricher (Choke) closer, from the getgo.  Moving the Alt / Battery switch unit will also allow them to be closer.

Thank you for your kind words - Its easy to be critical but in the end the "clever" pilot works with what he has - pegs, in this instance are cost effective, light weight, do not require reengineering/wiring and easy to use.

[Blueadventures]

Just now, skippydiesel said:

Thank you for your kind words - Its easy to be critical but in the end the "clever" pilot works with what he has - pegs, in this instance are cost effective, light weight, do not require reengineering/wiring and easy to use.

My comment is directed at the builder, yourself and it is an easy fix if you want to do it.  I would not accept the use of pegs like you have.  It's not good in my opinion.  Even change out the enricher device.  I have seen setups where the enricher is pull to 'ON' and a 90 degree turn locks the position.  After starting it is turned 90 degrees opposite and it springs to fully off.  You should consider such / similar.  You have asked assistance / comment with many things for your build and this is my comment to help.  Its not a direction just a comment.

[onetrack]

I'm not sure I'd be using items such as pegs in an aircraft. What if one slips off, or out of your hand, particularly in flight? - and lodges in a position where it cannot be retrieved, or is extremely difficult to retrieve?

Coins are notorious for lodging in control systems and causing disasters or near-disasters, pegs are likely to be up there with stray coins.

[BrendAn]

You don't need the choke for more than a few seconds in a 912.  Engine fires then slowly push choke back in

. don't see why you need to keep it pulled out like that.

 

[Bruce Tuncks]

In the Jabiru, the engine will not start if you have the throttle open and try and use the choke. If you try to put it away too soon, the engine stops. You need to run it for about 20 seconds before you can shut down the choke.

[old man emu]

Geez! Critics. I might be a nut, but when I read the original post, and having met Skippy, I simply saw it as a bit of humour. 

 

I was going to suggest these:  Only $3.24 a pack from your local Officeworks store.

 

When not in use, the clip can come back over the shaft of the handle and be out of the way.

[skippydiesel]

"What if one slips off, or out of your hand, particularly in flight?" - , slightly odd comment, - the choke is not used in flighty (or at least I have never done so) so a your concern is moot.

 

Rotax 912 ULS starts easily on full choke a (which includes a slightly elevated engine speed) however it is desirable to reduce to about 1/2 choke within a few seconds (the engine note will guide the pilot). There is then a (only) slightly longer few second and the reaming choke can be opened.

 

The choke actuating cable (it has Siamese ends for the twin carburettors)) is a  certified unit (not as per my last aircrafts adaptation from a motorcycle). The carburettor return (open) springs are quite strong so the "button" will literally snap back into the open (in) position if not held in place.

 

I reperched alternative Siamese choke actuators and only found one  (in the US) that had any sort of stay closed ability - not in production at the time.

 

The two pegs fit perfectly on the choke button shaft giving full rich & increased RPM  for start up and  then with the removal of one 1/2 open for on going engine running again engine note will guide the pilot for removal of last peg. They are easily & safely stowed for flight.

 

Of course the pegs need not be used but then one hand is fully occupied for the short start period leaving the other to perform such tasks as the pilot may require - having both hands free makes a significant & welcome improvement. It is far easier to know with certainty that the choke is fully closed (without having to have your hand there) - start, listen for the engine note (smooth out) change, remove one peg (& stow) leaving partial choke while monitoring/reacting too  RPM, oil pressure, EGT rise, listening out/responding, etc etc. The last peg can be removed & stowed without hast a little while after initial start.

 

The pegs also give a high visibility indication of choke position - a friction or 1/4 turn locking, devise may not be quite so obvious, resulting in reduced engine power and elevated fuel consumption

 

For this person, multi tasking is possible, despite my masculine handy cap but any little aid to reduce the burden  is welcome.

 

[onetrack]

Yes, my apologies, my wording wasn't really good enough, I was referring to "flight" as including the starting procedure, where you were actually commencing a flight, and a peg fell off.

Being on the ground still, even though the engine is running, is better than being airborne, and losing a peg in the cabin.

[cscotthendry]

You need one of these.

The handle is the choke pull. The red button is the start button.

Unfortunately it's a custom item made by Aeropilot, but someone could probably make something similar for you.

 

[IBob]

I have a separate choke that springs back: it's the silver knob at the lower left in the pic.

The starter switch is just under the throttle, and it works fine for me: throttle closed, fully pull choke, hit the switch, and as soon as she fires my hand goes from switch to throttle. Pause a moment, then feed in some throttle while letting the choke off.

My engine does have the timed spark retard, and that makes for much better starting than the earlier arrangement where the spark was advanced as soon as the engine hit a certain RPM.

I also have a heavy negative cable from engine back to battery: some years ago i read something from an Australian Rotax guru, who reckoned he had noticed a strong correlation between aircraft with starting/sprag clutch damage problems, and aircraft that relied on the hull for the negative return.
A combination of the above has always given me very good starting.

Edited December 5, 2022 by IBob

[cscotthendry]

 

2 hours ago, IBob said:

...

I also have a heavy negative cable from engine back to battery: some years ago i read something from an Australian Rotax guru, who reckoned he had noticed a strong correlation between aircraft with starting/sprag clutch damage problems, and aircraft that relied on the hull for the negative return.

 

Bob:

The negative return cable from the engine and every piece of electrical equipment on board, is a MUST. If anyone wires an airplane like cars are wired (using the frame for ground returns) they WILL have starting problems as well as radio problems somewhere along the line.

Every, that is every piece of electrical equipment on board an airplane, big or small, must have its own negative return wire of the correct amperage rating, to a single common ground bus point, no exceptions and no sub-bus points.

[skippydiesel]

IBob - I second csotthendry  and would go one further - it is false economy to persist with a weak battery. The reduced cranking amps (even if you do get the engine started) overheats the starter motor and where fitted will shorten the life of a spragg clutch. In Rotax the engine should spring to life within 12 -revolutions of the prop. I only ever give a battery one chance, charge over night, if it gets weak again its replaced.

[IBob]

CScott and Skippy....no disagreement with any of that!

And no reason for a newer 912, properly installed and wired, to be hard starting. However, the older ones without the timed spark retard could be nasty: supposedly the spark advanced once the engine reached 650RPM, but the crude circuitry of the ignition module measures that in an odd way, and having seen them 'spit back' on many occasions, I'm not convinced it does it well or accurately. The newer modules have been a huge improvement.
At the other end of the process, I get clean shutdowns too. I fitted a stop at my throttle quadrant bar, so that the throttle can be pulled back quite firmly without risk of bending the carb throttle arms, which are light in construction. At shutdown I first go to 3000 and run a mag check (not a very demanding test with warm modules, just a habit I picked up from another flier), then back to about 2000RPM. Then two fingers on two ignition switches, pull back firmly on throttle and switch off ignitions promptly, 1 then 2 as soon as RPM falls. This almost always gives me a clunk-free stop.
A lighter prop also helps in this, though mine is a 70" Bolly, so not particularly light.
 

 

[Blueadventures]

3 minutes ago, IBob said:

CScott and Skippy....no disagreement with any of that!

And no reason for a newer 912, properly installed and wired, to be hard starting. However, the older ones without the timed spark retard could be nasty: supposedly the spark advanced once the engine reached 650RPM, but the crude circuitry of the ignition module measures that in an odd way, and having seen them 'spit back' on many occasions, I'm not convinced it does it well or accurately. The newer modules have been a huge improvement.
At the other end of the process, I get clean shutdowns too. I fitted a stop at my throttle quadrant bar, so that the throttle can be pulled back quite firmly without risk of bending the carb throttle arms, which are light in construction. At shutdown I first go to 3000 and run a mag check (not a very demanding test with warm modules, just a habit I picked up from another flier), then back to about 2000RPM. Then two fingers on two ignition switches, pull back firmly on throttle and switch off ignitions promptly, 1 then 2 as soon as RPM falls. This almost always gives me a clunk-free stop.
A lighter prop also helps in this, though mine is a 70" Bolly, so not particularly light.
 

 

Agree with throttle stops to look after carbs.  Also if I don't fly for a couple of weeks I put battery on charge while I do the DI and this peps up the battery with a bit of charge.  No good starting with an under voltage battery; strains things electrically.  Re enricher position, my comment was also to get them closer so operate with one hand.  One option is to move the alt / Batt switch and place them away or something else.  Yes; bit of extra work but as not considered by builder (either Skip or original) then it needs enhancing.  Pegs can only be considered as temporary one or two flight thing not permanent.  What is the setup in his factory builds that he sells, should have copied that.  Cheers.

[IBob]

Blueadventures, I believe the throttle bar stop may go some way towards maintaining carb synchronisation.

I have the standard setup, with two cables coming from the quadrant bar to the two carbs. Initially, as this bedded in, and as expected, the carb sync required periodic minor adjustments. But since approx the 45hr mark, no further adjustment has been required: I still check it periodically, but it will be almost 200hrs since I last adjusted it.

I put that down to careful routing and securing of the cables and the throttle bar stop, which prevents the carb arms being pulled beyond the carb arm stops. And I would count it as one of a very small handful of worthwhile improvements to the Savannah build.

 

The Savannah throttle bar has a centrally placed quadrant, presumably for those wishing to put in a centre knob throttle, but otherwise unused. This comes back and strikes a block of MDP, cut to thickness once I had everything else in, and riveted to the firewall. In the pic you can see the MDP block, it is white and just to the right of the voltage regulator, with the unused quadrant resting againts it.

Edited December 6, 2022 by IBob

[RossK]

After reading this thread, I'm now further enlightened at how special the Sportstar is 🤩

You pull the choke all the way out and there it stays until you push it back in.

Actually, you can set it to any position and there it will stay, until further human intervention.

Thanks Skip for making me like my aircraft just a little more today 😁