Revisiting the Twin Comanche issue...

Aztec Driver said:
So I am now re-revisiting this issue.

I am faced with one of two legal possibilities. I cannot decide which I would like to do.

1. Leave it the way it currently is, meaning leaving it in compliance with Service Letter 558 from Piper.

2. Remove all modifications and rerigging all control surfaces back to the original factory specifications.

I know from experience that the airplane lands much easier with the stabilator rigged to the original specs. I just don't know what removing and rerigging will do to the handling characteristics of the airplane and whether it will be a serious detriment to the resale value of the aircraft.

Service Letter 558 adds stall strips to the front of the wings, a rudder gap seal, and a rudder- aileron interconnect to the aircraft. It also rerigs the control surface limits to move the ailerons up 1*, the rudder to the right 1*, and limits the up travel of the stabilator by around 6*. These are all supposedly to "improve the low speed handling characteristics" of the aircraft. I attached a copy of the Service Letter.

I would be afraid that, if I sold the aircraft to someone who may use it as a trainer, there may be problems because of this.

From all of the information I can dig up on this, all of these modifications were done to fix a nonexistent problem brought on by the training environment of the time.

Can anyone enlighten me as to the purpose of each of the changes, especially the rerigging of the control surfaces?

I assume the airflow strips change the airflow in a stall to allow the use of the ailerons.
The interconnect is to keep the aircraft coordinated in a stall to prevent a spin.
The stabilator limit is to keep the pilot from driving it too deep into a stall too quickly, I assume.
The others I can only assume will also help in handling during a stall.

I don't really want to remove the airflow strips, as that would require refinishing the leading edge. I also assume the removal of the interconnect is not a quick and easy task.

Anyone have any other thoughts on this?
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Byron,

This is largely a repeat of my response on the Airworthy Comanche Forum on Delphi. http://forums.delphiforums.com/comanches/start

I have a twin without the kit installed. As far as I know, it was never installed, but might have been removed when they installed the deicing system back in 1992.

The plane flies fine without it on one engine, and I like the handling characteristics better without the kit installed. IMO, it was just another clumsy attempt to solve a marketing problem with eye wash. The problem was that instructors were having their students hang the aircraft on the props and then failing an engine. The FAA seemed to think that was a good idea too. The solution was to quit doing that maneuver.

As for the landing characteristics, either the tail stalls or it runs out of authority. The first thing to do is not to be hot crossing the fence. Modern orthodoxy in flight training is to hang on to blue line until you cross the fence. That is pretty much guaranteed to float and drop a Twinkie. 75lbs of lead shot against the back bulkhead helps a lot, as does keeping in a schosh of power until touchdown. Those are the cheaper things to do. The wing trailing edge fillet from Knots2U gets good reviews from owners as smoothing the airflow over the tail.
 
Kristin said:
Byron,

This is largely a repeat of my response on the Airworthy Comanche Forum on Delphi. http://forums.delphiforums.com/comanches/start

I have a twin without the kit installed. As far as I know, it was never installed, but might have been removed when they installed the deicing system back in 1992.

The plane flies fine without it on one engine, and I like the handling characteristics better without the kit installed. IMO, it was just another clumsy attempt to solve a marketing problem with eye wash. The problem was that instructors were having their students hang the aircraft on the props and then failing an engine. The FAA seemed to think that was a good idea too. The solution was to quit doing that maneuver.

As for the landing characteristics, either the tail stalls or it runs out of authority. The first thing to do is not to be hot crossing the fence. Modern orthodoxy in flight training is to hang on to blue line until you cross the fence. That is pretty much guaranteed to float and drop a Twinkie. 75lbs of lead shot against the back bulkhead helps a lot, as does keeping in a schosh of power until touchdown. Those are the cheaper things to do. The wing trailing edge fillet from Knots2U gets good reviews from owners as smoothing the airflow over the tail.
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I've always thought that stupid and never fly that way. I keep it above redline until I have the runway made and slow down from there.
 
I think a lot of the problem is understanding when you have the runway made. Inexperienced flight instructors have been interpreting that to mean when you cross the fence. In truth, it is at least half a mile out as an engine failure at that point or closer just means you put some more power on the good engine and get it on the runway. It is the same sort of rote learning that has instructors telling students on a complex check out that "no runway remaining" is when the plane crosses the departure end of the runway.
 
I'd agree with Kristin, most people don't have a good understanding of "runway made", instructors included. As with most procedures, they're put in place for the lowest common denominator.

On a long runway, I keep blue line until runway is made and then slow down, aiming for my 1000 ft touchdown. On a short field, I keep closer to red line and aim for the numbers.
 
I am in the habit of slowing at the half mile point. This usually coincides with DH on the precision approach so I am used to changing configurations and speed. The Comanche doesn't use the barn door flaps that you find in Aztecs and Navajos, to name a couple, so when flying them, that is usually where I drop full flaps thus committing myself to land if one fails. At half mile, you have the runway made as you should be aiming 500-1000 feet down the runway and if you just add power on the good engine you will cross the threshold with one windmilling.

This is not the only way to fly! Just my way! :)
 
That's probably what amounts to what I do. Honestly I don't quantify it as much in distance numbers, more quantified in terms of "Yep, that's about right." :)
 
My eyeball isn't that calibrated either, but for purposes of explaining, I think it about close enough. I have shot enough ILS approachs so have DH/1/2 mile is what looks about right.
 
Fearless Tower said:
Interesting - when I was flying the Twinkie, I found that I got my best landings by trimming slightly nose UP on final (to where I would hold a slight forward pressure on the yoke to maintain blue line on short final. Then pull power add slight back pressure on the yoke and I could consistently grease it on the mains.
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On final, the key is 4 full turns of nose trim up, but hold the pitch attitude down until you arrest your scent and hold it off till the mains touch the runway
 
Hello everyone! Thanks for a useful thread for me to read. New to this forum so please bear with me. A flight school I work with has a Twin Comanche with a Stab rigging issue with the 4.5 deg leading edge up travel. Here is the issue:

The Comanche was sent to an avionics shop to have an S-TEC auto pilot installed. After the auto pilot was installed, the mechanic attempted to rig the stabilator and set the tensions. The problem he is having is that he can get the 15.5 deg leading edge down travel on the Stab (making contact with the adjustable stops in the tail cone), BUT he cannot make the 4.5 deg travel up before the torque tube balance weight contacts the rubber bumper in the fuselage (the balance weight contacts the bumper at 3.9 deg).

1) Has anyone seen this problem before?
2) AMM gives a 1 deg tolerance. Can I adjust the stop bolts in the tail to get 3.5 or greater as long as the balance weight is clear of the stops, and as long as the stops in the tail are the first to contact?

Thanks for helping!

Kevin
 
Don't know anything about your problem, but if you want to know the quality of advice you're going to get here I crashed with the OP in his Twinkie.
 
steingar said:
Don't know anything about your problem, but if you want to know the quality of advice you're going to get here I crashed with the OP in his Twinkie.
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Holy necro update The OP crashed his Twinkie? Guess that's why he's an Aztec driver lol.
 
Kristin said:
It is the same sort of rote learning that has instructors telling students on a complex check out that "no runway remaining" is when the plane crosses the departure end of the runway.
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I completely agree. There's lots of crap instruction out there, very people actually think or understand much about aviation, they just go through the rote motions and hopefully if the **** hits the fan it's enough to keep them alive

Two different people I flew with recently kept the gear down even though we were practically at pattern altitude already and crossed the end of the runway. The "no more runway remaining" was very literal. Whatever happened to "positive rate, gear up" - do we have such little faith in our planes and in ourselves for quick thinking that we elect to leave extra drag hanging out there for as long as possible?
 
Also.. we really need a tombstone icon or something next to a thread for when it's brought back from the dead
 
There’s a twin Comanche for sale at my home airport (that’s right, it’s MY airport). I don’t know anything about it other than it’s for sale and I met the owner the other day. Also there’s no link to any for sale page so I’m not sure how any of this is helpful in any way.
 
eman1200 said:
There’s a twin Comanche for sale at my home airport (that’s right, it’s MY airport). I don’t know anything about it other than it’s for sale and I met the owner the other day. Also there’s no link to any for sale page so I’m not sure how any of this is helpful in any way.
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Tantalum said:
Also.. we really need a tombstone icon or something next to a thread for when it's brought back from the dead
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They already have a big RED box with a "yes, I understand I'm going necro" button. That should be enough to keep the dead threads dead.
 
Ravioli said:
They already have a big RED box with a "yes, I understand I'm going necro" button. That should be enough to keep the dead threads dead.
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True, but then an idiot like me clicks on a thread thinking it's something new and I get 2 pages in until I realize it's from like 2014 or something
 
flyingcheesehead said:
Nope... Aztec crashed first. Engine failure on takeoff from a really short strip, put it down in a neighborhood and lived to tell the tale.

@steingar what happened in the Twinkie?
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WV62 is a 3K strip in the Canaan valley in West Virginia. Plenty long, though there are lots o ufsquirrely winds there. We were doing some flying at a POA do, and I went in his Twinkie. I don' think i'd ever flown in a twin before that. He came in hot and high. Told him I'd go around. I fly neither a Comanche or it's Twin Cousin, but in my Cherokee that approach looked all wrong. He got it stopped by the end of the runway, but not without some drama. He said he wanted to do that again. We came in on speed and altitude the second time. The tire blew on the port main landing gear, he lost directional control, and the aircraft veered left and wound up in a ditch. All of us got out there, pulled it out and walked it to parking (someone had a furniture dolly that was a big help). Mechanic few in the next day, changed the tire and he flew home.

Thinking about it now, I'm pretty certain both those engines were running when we hit the ditch. No damage to the props though. Don't know if I'd have flown it, but it wasn't my airplane. Bryon is flying for pay these days, or at least he was last time I heard.
 
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Bill Jennings said:
Don't forget that we had to drop it on over some pretty tall trees at the end of the runway, THAT is what made this airstrip interesting.

https://www.pilotsofamerica.com/community/threads/windwood-resort-292-pics.31785/
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Wasn't the trees that gave me pause, that's pretty normal where I come from. The ones at DUH are taller. The winds were nutz. The one time I flew my Cherokee I did a go around and told Mrs. Steiingar that if it didn't work the second time we were going elsewhere. I like you guys, but not enough to prang my airplane. As it is it took every inch of that runway to land my aircraft. Winds were crazy that day. Gary just about porpoised his baby Beech. I'd think twice about taking the Mooney in there. Not on a day with those winds, I can tell you that. The Do's were nice though, it's a pretty spot and we found plenty to do.
 
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