To Trim or Not to Trim

[Bladestrike]

For those of you flying twins, I started a rather heated debate over on pprune re: trimming your turns.

It started when an ex-mil guy gave me some grief over using the hat for turns. The belief is, should you feel some vertigo, let go of the stick and she''ll right herself. I believe that you''re saturating the channel and getting very little aid from the AFCS throughout the turn, and fighting the system, contrary to its intended design. Sikorsky agrees with this but it does come down to personnal preferance. Apparently the US Navy fight the force trim and the Army boys trim. Whadayathink?

 

[CTD]

Depends on the aircraft and autopilot system. Some will attempt to counter your input and would cause more trouble.

Personally, I like to trim for what I''m doing, and I fail to see how letting go and rolling wings-level will solve your problem with the leans - it might make your workload increase when ATC starts asking you what the hell you''re doing.

That''s why there are two of you in the office.

 

[Xnr]

Hey Bladestrike

I told you that you were doing it all wrong on the other forum no matter what Nick says.

 

[Rotorhead]

Hey Buddy,

You didn't take enough heat over at pprune, you want to start the whole thing over again? Yikes.

RH

 

[Bladestrike]

I thought I won over there???

 

[CTD]

Bladestrike - what was the general consensus on your inquiry? I assume we''re thinking along the same lines?

Sorry, I don''t frequent the other forum much anymore, read - at all. Too many egos masquerading as experts.

 

[Bladestrike]

Nick Lappos, Senior Sikorsky Test Pilot, agrees. He was on the design team for the 76 AFCS. It comes down to the design of the system. The intent was to make life easier, and most AFCS systems, if you recenter the stick into a turn, or trim the turn, the AFCS will provide full stabilization as intended around the stick position. If you move the cyclic against the trim, you near saturation of the AFCS and could negate its affects (although this varies on some newer systems). The other side use the force trim as an autoleveler. You let the springs give you an indication of the turn and if you get vertigo, you let go and the bird will right itself. While most dismiss that you would actually let go of the stick if disorientated, this is the way most military guys are taught. The design was to make life easier, and trimming a turn is much easier than fighting the springs. Try a 45 degree bank near Vmini with and without trimming the turn and see the difference. I don't see much sense in fighting the system for something that rarely if ever happens. If I'm trimmed in a rate one turn and get vertigo, I'll still be in a rate one turn. There's not much chance of losing control. Apparently its an arguement that has been going on since the inception of the force trim and even the US military don't agree. Army trims, navy doesn't. Most North Sea guys fight the trim, but then again, most of them are ex-mil and thats the way they were taught. In Canada in general, HeliJet trims, Cougar doesn't, the CAF doesn't, and there isn't a consensus among the boys with the red chicken. It generated quite a reponse.

 

[reddog]

Bladestrike. As stated above, by CTD I think, it does depend on the aircraft and the AFCS or autopilot installed. If I recall correctly, one of the eleven "prohibited" maneuvers (sp?) in the Super Puma Flight Manual is trimming into turns. Flying a turn against the trim in the Puma worked well and was quite easy. The S76 on the other hand it doesn''t really seem to make much difference either way. I just got back from flying the Ch-146 simulator and it gives you an "autotrim" warning light if you attempt to fly against the trim. Go figure!

 

[RDM]

Reddog, having a look and can not find it in the FM, thought it was in the SOP''s , although I do not have the full FM home with me, will check later today.

I would say about 50 50 here with regards to trimmimg,

Like CTD said, that is why there is two in the office

 

[Bladestrike]

Thanks for the responses. Let me know if you find anything in the AFM. I''m back to work Tuesday and we have a few sitting around, I''ll look as well. If thats the case, it would explain alot.

 

[Xnr]

Blade

When your out over the ocean, miles and miles off shore,you can do as you please. But you are still doing it all wrong.

Cheers Buddy

 

[Rotorhead]

Bladestrike,

Are you in hibernation there buddy?

RH

 

[sharkbait]

While not having anything usefull to contribute:
I think I can tell a story obout why we fly against force trim:
A WISE MAN 🙄 , one dark and stormy night, once told me that:
In the bad old days when green 204s and 5s flew over the green jungle and everybody was shooting at everybody else---
There was no AFCS, just force trim and a high time driver was 700 hrs.
Because one of the pieces of metal flying around the country could hit you you flew with your shoulder harness locked so you did not fall forward over the controls when shot and you trimmed for level flight and flew against the force trim so that when one got shot the a/c would perhaps return towards level flight while your copilot sprang to the controls.
Because flying in clouds and in the dark was also scary they did the same thing only now they kept the harness locked in case they got hit by lightning as they did not have WX Radar.
Because doing what is familiar is comfortable:
When everybody got back to civilization the same basic type of helicopter got painted pretty colours AFCS and WX radar was installed. There were still a lot of people who were used to doing it the old way way so they just kept on trimming for level and wrestling the beast around. Aside from which REAL MEN didn't need no fancy outo pilot to tell them where to go.
Besides which the Chinese Hat on most 212s is super sensitive and tends to either attempt a moon shot or an outside loop ( attempt at humour ) so most people just avoided touching the @#$%^ thing.
When I asked the MOST WISE what was truth He looked at me, pointed to the AFCS wheels and turn selector on the centre consul, and said:
" Listen chucklehead: In Cloud or at Night: Use the AFCS Att Hold to do all the turns that's what they spent all the money to design, build and install it for !!!!"
He then went back to reading his book.

It was a good story and made sense to me - often times I find people do things on one type because thats the way they did it on the Bung VertiLeap 2000 they flew last year. Habit becomes SOP.

I find that if you have the AFCS in ATTD and you try to wrestle around against trim or use the roll wheel instead of the turn knob on a 212 you will soon get the darn thing severely out of trim and on the 76 the DAFCS light will come on and sometimes the outo pilot has to be reset, most annoying. I constantly hector my poor cockpit companions about it. 😀

Anyhoo that's the lighter side of it. 😀

 

[twitch]

If I remember my Super Puma stuff I think the restriction in the flight manual was "releasing artificial loads" was prohibited under IMC?

It works with the 332 but Sikorsky's handle much better trimmed, in my opinion.

twitch

 

[Blackmac]

I tried trimming out my loved one using love handles, didn't work , so I just hung on for dear life. OHHHHH MYYYYY God.