I had an interesting trim incident today. How many people actually check their trim indication to the physical position on their walk around? I am embarrassed to say I don’t but will do so after today. Pre-take off check, I trimmed for slight nose up per the trim indicator only to discover that as I lifted off the nose kept coming up and required a small amount of muscle and lots of fast re-trimming to sort things out. Lesson learnt.
On a happier note, I jumped in at the deep end and went off to Lydd to fly the Rnav and ILS/DME procedure on the new kit. Went very well and I was most happy generally. I just need to re-visit the Aspen tutorial to sort out one small issue but for the rest it was good – hmmm, that sounds a bit cocky, sorry. :-) I hand flew the ILS/DME and let the auto pilot fly a chunk of the RNAV, Hang, autopilots are the dogs bollocks and allow for so much additional capacity when flying single pilot. My fear is I might not want to go back flying the steam gauges again…………… :-)
I am still undecided about the traffic awareness thing. the lady in the box kept bleating at the most inconvenient time and took a few seconds to process that it was not ATC bleating. I switched it off landing back at Shoreham as her voice was getting hoarse from calling all the traffic.
Few pictures below:-
Bloomer wrote:
I had an interesting trim incident today. How many people actually check their trim indication to the physical position on their walk around?
I do! Never did, until one day flying with instructor/DPE friend, he pointed out to me that while the trim was set correctly (I looked back over my shoulder, doable in a Cessna), it was nowhere near the marking. Lesson learned – now check during walkaround AND during the ‘free-and-correct’ check during runup by looking back (I know, that’s not an option in many airplanes).
But what was wrong about the trim? In fact, what could go wrong about it anyway, except a broken or loose cable (assuming bowden cable control, which I think is almost universal)?
Hi Jan.
My guess is that the indicator had either got stuck or had shifted on the cable as the trim itself worked fine it was just finding the correct spot before lift off. Once in the air it was no longer an issue and I left it where it was on landing so it was less of a problem on next take off. The engineers will look at it at the same time they sort the nose oleo out. That collapsed at Lydd so I could not go onto to Pent Farm for fear of a prop strike on the grass runway. Aviation eh. 
Huh, I hadn’t realised some planes have a separate indicator for the trim. How complicated some people can make life! On my little craft the trim control serves as an indicator at the same time. Actually I do not need to look at it, the feel is a perfect indication. It is cleverly arranged next to the flaps control and most of the time both are aligned. Except on a plane like a DC3, where the trim control is a wheel, I can’t see the need for anything more complex. But, like as not, I am again seeing things too simple – too much from my own point of view.
The Piper PA28 trim system (and used in many other Pipers) is a cable wrapped around a drum in the cockpit and the same in another drum in the tail operating a screw jack.
The indicator is a small piece of wire, bent, twisted and soldered into shape. It pivots on a screw below the cockpit drum with its position dependent on which ‘ring’ of a scroll it sits in on the side of the trim wheel. Not only can the trim indicator get bent out of position but it can also foul on the trim wheel or the trim wheel plastic cover.
In my previous life, the company’s procedure for setting take off trim, was by winding the trim all one way (nose up, I seem to remember) and then so many turns in the other direction. I can’t quote the actual number of turns as I forget what it is now. Allowance being made with experience for flying solo, two, three or four up – or with bags in the back.
Obviously, it’s important to check full trim operation on the pre-flight but one should also watch the indicator move in the slot at the same time – it should go from one end to the other of the slot.
Jan_Olieslagers wrote:
Huh, I hadn’t realised some planes have a separate indicator for the trim. How complicated some people can make life! On my little craft the trim control serves as an indicator at the same time.
It’s an interesting point. My airplane has a separate indicator for trim that reads directly from the horizontal stab (via cable). Isn’t that a good thing? An independent reading of the actual position of your trimmable stab, rather than a “fake” trim position indicator that is more a “trim wheel position” rather than a “trim position”.
You have a point in the sense that it is another system that can fail, which happened to the OP.
Btw. nice Aspen + Garmin setup! What Garmin is it? (I have trouble recognising the later models)
Hi Archie.
It is a GTN 750.
The purpose of a trim position indicator is to enable it to be checked pre-takeoff. On some (many?) types it is not humanly possible to overpower a maximally out of trim setting, once above Vs.
That still doesn’t protect you in a crappy autopilot installation which can get accidentally engaged pre-takeoff and wind the trip all the way back during the takeoff roll (a famous Cessna crash).
aerofurb wrote:
In my previous life, the company’s procedure for setting take off trim, was by winding the trim all one way (nose up, I seem to remember) and then so many turns in the other direction.
That’s what I do, actually before shutting down. I once had the trim indicator jump out of position, didn’t notice, had a bit of a scare on take off.
