Simviation Forum - Typical pitch trim settings for Cherokee 180

May 14^th, 2010 at 1:27am

snippyfsxer Offline
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I'm curious what some typical trim settings would be for a Cherokee 180, with two people up front. The Carenado Cherokee requires about 50% up trim for takeoff, 0 trim for cruise, and about 90% trim up for landing at 80mph (69 knots), full flaps.

In the real plane, are those figures realistic?

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Reply #1 - May 14^th, 2010 at 5:37am

RitterKreuz Offline
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snippyfsxer wrote on May 14^th, 2010 at 1:27am:

In the real plane, are those figures realistic?

not even remotely

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Reply #2 - May 14^th, 2010 at 5:57am

Brett_Henderson Offline
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The (real) PA28 is a little nose-heavy.. especially when flown by a sole occupant... but nothing requring that amount of trim.

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Reply #3 - May 14^th, 2010 at 7:16am

snippyfsxer Offline
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Brett_Henderson wrote on May 14^th, 2010 at 5:57am:

The (real) PA28 is a little nose-heavy.. especially when flown by a sole occupant... but nothing requring that amount of trim.

Looks like I discovered the fine art of FDE fiddling just in time then!

Any ballpark figures on what ranges one might encounter in the real thing?

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Reply #4 - May 14^th, 2010 at 8:30am

Brett_Henderson Offline
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Unless it's a Cherokee with which I'm intimately familiar.. I'll set the trim neutral, no matter the load.. and then start my trim-groping while climbing.

Again.. if you're the sole occupant, and try to fly a text-book approach, you'll have a good amount of trim at first.. but it will be nearer to neutral, as you deploy flaps.. and is never a significant amount.

The problem with MSFS trim, is that it's not trim.. It's more like a range selection. Let's say that an elevator has a 30-degree range (15-up, 15-down). Proper trim would allow you set the elevator somewhere in that range so that it will stay there, hands-off. MSFS trim just moves the range. Like.. nose-up trim would just make the elevator range change,, I.E.. 20-up, 10-down.. so that hands-off elevator deflection is now +5 (even if you're parked on the ramp).. and at this trim setting, you have less down-deflection available. And of course the reciprocal is true. Nose-down trim not only sets hands-off elevator deflection negative, it ALSO takes away some of the available up-deflection.

I'm sure you've encountered a model where rotation was near impossible until adjusting the trim "up" ? That would never happen for real. It would require more force on the pilot's part for rotation.. but it would NOT take available up-deflection away.

Accepting this MSFS limitation just reinforces how important it is to have the model's flight-dynamics set up properly (so that you'd never need significant deflection, either way). But even the best-tuned dynamics in the MSFS world will still leave you with an airplane that will be glued to the runway, if there's too much down-trim.. Cheesy

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Reply #5 - May 14^th, 2010 at 9:14am

olderndirt Offline
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Brett_Henderson wrote on May 14^th, 2010 at 8:30am:

Unless it's a Cherokee with which I'm intimately familiar.. I'll set the trim neutral, no matter the load.. and then start my trim-groping while climbing.

Again.. if you're the sole occupant, and try to fly a text-book approach, you'll have a good amount of trim at first.. but it will be nearer to neutral, as you deploy flaps.. and is never a significant amount.

The problem with MSFS trim, is that it's not trim.. It's more like a range selection. Let's say that an elevator has a 30-degree range (15-up, 15-down). Proper trim would allow you set the elevator somewhere in that range so that it will stay there, hands-off. MSFS trim just moves the range. Like.. nose-up trim would just make the elevator range change,, I.E.. 20-up, 10-down.. so that hands-off elevator deflection is now +5 (even if you're parked on the ramp).. and at this trim setting, you have less down-deflection available. And of course the reciprocal is true. Nose-down trim not only sets hands-off elevator deflection negative, it ALSO takes away some of the available up-deflection.

I'm sure you've encountered a model where rotation was near impossible until adjusting the trim "up" ? That would never happen for real. It would require more force on the pilot's part for rotation.. but it would NOT take available up-deflection away.

Accepting this MSFS limitation just reinforces how important it is to have the model's flight-dynamics set up properly (so that you'd never need significant deflection, either way). But even the best-tuned dynamics in the MSFS world will still leave you with an airplane that will be glued to the runway, if there's too much down-trim.. Cheesy

Brett, I knew that MSFS trim was like a dog chasing it's tail but that was a revealing explanation - thanks

.

THIS IS NOT A PANAM CLIPPER

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Reply #6 - May 14^th, 2010 at 8:25pm

skoker Offline
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When I flew we set it to 20% and forgot about it. Wink

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Reply #7 - May 14^th, 2010 at 9:45pm

olderndirt Offline
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skoker wrote on May 14^th, 2010 at 8:25pm:

When I flew we set it to 20% and forgot about it. Wink

Curiosity forces me to ask - 20% of what?

THIS IS NOT A PANAM CLIPPER

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Reply #8 - May 18^th, 2010 at 4:41am

FridayChild Offline
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Brett_Henderson wrote on May 14^th, 2010 at 8:30am:

The problem with MSFS trim, is that it's not trim.. It's more like a range selection. [...] Nose-down trim not only sets hands-off elevator deflection negative, it ALSO takes away some of the available up-deflection.
I'm sure you've encountered a model where rotation was near impossible until adjusting the trim "up" ?

This finally explains it for me! I knew there was something weird with the trim in FS. Thanks!

Founder of A.A.A.A.A.A.A. (Aircraft Amateurs' Association Against Absurd Aviation Acronyms) My system specifications: FLIGHT SIMULATOR 2004 - AMD Athlon 64 3200+ CPU - 3 GB PC-3200 DDR400 dual channel RAM - 500 GB Seagate Barracuda 7200 rpm SATA-II hard disk - Sapphire Radeon HD 5750 1 GB PCI-E graphic card - Logitech Wingman Force 3D joystick + Logitech Formula Force pedals My FS whereabouts: low and slow, small single engine prop GA, Italy airfields.

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