Using Trim to Climb?

[SkyChaser]

To everyone saying, "Just maintain the seat tracks better", say you're a renter. Is this something you can tell by looking at the seat tracks? Can you tell that failure is imminent if you aren't the one maintaining it? I totally get wanting to stop the problem as its root, but unless it's something I can see from a visual inspection, I may not be able to tell that the seat tracks are about to give way.

 

[Brad W]

great point I think Skychaser. Same thing applies to almost everything in the plane..under the cowling and under the inspection plates. You have to trust the A&P unfortunately.

 

[Palmpilot]

There's a Dakota that I used to rent, and the seat would slide back on climbout an almost every flight, in spite of my efforts to lock it firmly in place. Fortunately, it never slid back far enough for me to lose access to the controls. I never felt the urge to try to use the controls to stop myself from sliding; not sure why.

 

[Dan Thomas]

Is there another AD that required the installation of those little stops to limit travel so that it can't go forward or aft off the rail?

The seat stops are mentioned in that same AD:



They don't need to specify what stops, or how many. That's the job of the FAA-Approved parts catalogs.

Note also how the seat lock pin engagement measurement is taken in Item (10). With the front of the seat lifted up as it would be under acceleration and the pilot's body pressing on the seat back, the engagement is measured. This is work, in a confined space, and measuring it is a pain, and anything that is a pain is often shortcut by mechanics. So if that pin's engagement is a bit short, and the holes are worn so that the aft edge of the hole has a slope to it (you've all heard the pin clicking on those holes as you slide the seat back, and that's caused by a bent actuating lever, more substandard maintenance), and the pin itself can get a slope worn on it, and that all adds up to a pin that can pop out and let the seat go. A weak pin spring just makes it happen so much easier.

Like I said, an AD is legally binding. And this AD is repetitive, every 100 hours or 12 months, whichever comes first. From what I've found I can see that some mechanics see if the seat locks, and they just sign off on the whole AD. No detailed analysis as required by law.

 

[Dan Thomas]

There's a Dakota that I used to rent, and the seat would slide back on climbout an almost every flight, in spite of my efforts to lock it firmly in place. Fortunately, it never slid back far enough for me to lose access to the controls. I never felt the urge to try to use the controls to stop myself from sliding; not sure why.

You shouldn't have kept renting that airplane. AFAIK there's no AD on Piper seat rails, but an event like that needs to be reported, loudly, and a threat to take your business elsewhere if they can't do better than that.

 

[Dan Thomas]

To everyone saying, "Just maintain the seat tracks better", say you're a renter. Is this something you can tell by looking at the seat tracks? Can you tell that failure is imminent if you aren't the one maintaining it? I totally get wanting to stop the problem as its root, but unless it's something I can see from a visual inspection, I may not be able to tell that the seat tracks are about to give way.

If you're renting you might want to use those FAA-PMA seat locks shown earlier. Buy a set and keep them in your flight bag. But if both seat rails have stops in them, and some airplanes do, you'd have to remove a stop to put them on. That's more hassle.

Or find a friend that's an A&P and take him along on a flight sometime and get him to look at stuff.

 

[Lindberg]

Part of my passenger brief in the Cessna is always to warn about the possibility of the seat sliding back. And to tell the passenger that they may grab anything they like in the cockpit in the event that their seat slides back, except that they may not grab the yoke because if they grab the yoke we will die. I gave this briefing to one passenger who seemed perfectly fine until we were in the air and I offered to let him fly the plane. I told him to go ahead and grab the yoke, and he freaked out. I couldn't figure out why until he said, "You told me if I grabbed that we would die!"

 

[Palmpilot]

You shouldn't have kept renting that airplane. AFAIK there's no AD on Piper seat rails, but an event like that needs to be reported, loudly, and a threat to take your business elsewhere if they can't do better than that.

The problem has been squawked. Most of the club's planes are well maintained.

 

[Clip4]

To everyone saying, "Just maintain the seat tracks better", say you're a renter. Is this something you can tell by looking at the seat tracks? Can you tell that failure is imminent if you aren't the one maintaining it? I totally get wanting to stop the problem as its root, but unless it's something I can see from a visual inspection, I may not be able to tell that the seat tracks are about to give way.

The seat tracks don’t give way, the holes for the locking pins are elongated or cracked allowing the locking pins to disengage.

Every thing about the seat should be correct. The seat back adjustment puts the seat in the vertical position so you aren’t flying ghetto style. The seating positioning mechanism works properly. The spring isn’t worn out and the seat quickly and firmly locks into position.

 

[Half Fast]

To everyone saying, "Just maintain the seat tracks better", say you're a renter. Is this something you can tell by looking at the seat tracks? Can you tell that failure is imminent if you aren't the one maintaining it? I totally get wanting to stop the problem as its root, but unless it's something I can see from a visual inspection, I may not be able to tell that the seat tracks are about to give way.

Well, you can’t do the job of an A&P during your pre-flight, but if you’re worried you could do a few things to help your odds.

I know you fly with the seat all the way forward. Most pilots are excessively tall compared to us, so the forward engagement holes are less likely to be worn. Before you’re seated, slide the seat back a ways and look at the forward holes, if you can see them. You might need a small mirror. Be sure they don’t seem elongated and worn. Not something to check every time you rent the same plane, just an occasional look. The wear happens slowly.

Next, move the seat forward, lift up on the front edge, and shake the seat a bit to make sure it doesn’t come off the rail.

Then once you’re seated, pay attention to the engagement of the adjuster. Do you have to move it all the way to get it to release, or does the seat slide as soon as you make a small movement?

Finally, teach @2-Bit Speed how to take off in case he needs to take over control for a moment.

 

[Dan Thomas]

Well, you can’t do the job of an A&P during your pre-flight, but if you’re worried you could do a few things to help your odds.

I think most pilots could look at the seats, rails and locks in several airplanes and then tell me which ones look worn out or not locking very well. Study the AD first, then go and look at things for a while. The springs should be strong enough that they drive that pin into the hole with a bit of a bang.

An owner can do a few things to make stuff last longer. The AD forbids the lubricating of the rollers and their bushings, as it attracts dust that causes sludging up and binding of the rollers, but there is nothing in the AD that prohibits the use of a bit of paraffin wax on the undersides of the seat rail flanges where the roller housing tangs rub when you're in the seat and run it back. The wax will stop the galling that eats the tanks and rails. We find this in a 172 service manual:



And while you're at it, look at the plastic washers on each side of the seat rollers. They prevent the edges of the rails being galled away. In at least half of the airplanes I encountered, those washers were entirely shot, worn all away. The OEM Cessna washers are just scrap ABS plastic sheet, same stuff they used in interior panels, and it is not a wear-resistant plastic. McFarlane sells washers that are 100 times better, and cheaper, too. McFarlane has all the stuff to replace rollers and rails and stuff. I don't think they have the lock pins yet, which are $tupidly expen$ive from Cessna. I believe we paid close to $400 for one. A length of (probably) 4130 1/4" round bar with two or three holes drilled in it, one end tapered a bit, and bent just so. And there are many pin part numbers. Many different seats.

 

[Rgbeard]

Part of my passenger brief in the Cessna is always to warn about the possibility of the seat sliding back. And to tell the passenger that they may grab anything they like in the cockpit in the event that their seat slides back, except that they may not grab the yoke because if they grab the yoke we will die. I gave this briefing to one passenger who seemed perfectly fine until we were in the air and I offered to let him fly the plane. I told him to go ahead and grab the yoke, and he freaked out. I couldn't figure out why until he said, "You told me if I grabbed that we would die!"

It looks as if you've identified an area of improvement for your passenger briefings.