How does the friction adjustment on push-pull throttles work?

[abgd]

I'd always assumed there would be some sort of compressible washer that would grip the sides of the plunger more firmly as it was compressed. But I have to confess I never got round to dismantling one in a rental aircraft. In my own aircraft, when you unscrew the friction adjustment ring, it exposes a cylindrical chamber with exactly _nothing_ inside!

In practice it works acceptably well. The throttle will gradually work itself closed if you don't pay attention, but that's why they teach us to keep one hand on the throttle during take-off, isn't it... What it stops me from doing however, is pretending to be a test-pilot. How fast can I go at 2200 rpm, with what fuel consumption? I can't tell because I can't keep the rpm on target sufficiently accurately for any length of time.

Now, I understand I have to get my inspector to check over any control modifications, but I'd like to come up with a solution for him to rubber-stamp. Hence the question, what - assuming anything - should be in there?

[Whopity]

Its a Collet, a tapered sleeve which grips the spindle when the friction nut is tightened.

[piperboy84]

I prefer the Vernier type throttle control, seems to give more precise control options, screw it for very slight adjustments or work it like a syring for big movements.

https://en.m.wikipedia.org/wiki/Vernier_throttle

[abgd]

Thanks. I'll look into sizing a collet to fit. I agree with you when it comes to Verniers for mixture control, Piperboy, but I'm just looking to make the throttle that I have work a bit better.

[9 lives]

Perhaps abgd, the plastic collet is missing from your throttle lock. In this case, you'll know, as there'll be no locking whatever. If there's some, it's all there, but worn.

On the topic of throttles of that type, or indeed any push pull engine control cable, there should be (and you want to assure) "bounce" at the maximum power side of each engine control. The control can be felt to hit the engine end stop before it bottoms out on the panel. That way you know that you're getting full travel out of that control. If it bottoms out on the panel, you cannot be sure - it needs rerigging. Every now and then, give the throttle a heart tug in the "closed" direction. occasionally cables break, and you'd rather find that on the ground. I know two pilots who had the throttle come right out in their hand, cable and all, when they closed it in flight.

I am definitely not a fan of vernier throttles. Fine for mixture, and prop, but throttle must be able to be closed quickly with no obstruction. I'm not aware of any aircraft in which a vernier throttle was original equipment.

[dirkdj]

Vernier controls are standard on Beech Bonanza prior to 1984, I like them very much, you can push the control in quickly or make very fine adjustments by turning. You need to take the throttle in your hand so that the pushbutton part fits in the palm.

[abgd]

Hmm... I may just buy a new throttle assembly. I was hoping the part I'd need would just be a leather washer or something similarly generic.

I'm willing to be persuaded that Vernier throttles can be nice, but I'm not fitting one: it's just not that kind of aircraft.

[9 lives]

I was unaware that Bonanzas came with vernier throttles. Perhaps that aircraft type is a little more tolerant of that arrangement, but I still dislike the idea. The only aircraft I flew with a vernier throttle (later, unapproved installation) was a 185 floatplane. With no brakes, having to fumble to close the throttle is not good.

You need to take the throttle in your hand so that the pushbutton part fits in the palm.

Some vernier controls require the pushbotton to be nearly flush with the knob to release. That's less than easy with your palm. For most aircraft, the engine controls are much lower on the panel, and the geometry of one's wrist does not accommodate palming the button easily.

For prop and mixture controls in singles, I really like vernier controls. For throttles, I prefer "direct" control. It works on every PA28, and all twins just fine!

[dirkdj]

You actually extend your index finger to touch the panel, the throttle control is just the right length if you palm the button part, you can make quick but fine adjustments once you have discovered the secret.