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geneseib

geneseib

Line Up and Wait
Joined
Aug 11, 2008
Messages
792
Location
Eldridge, MO
Display Name
Display name:
Gene Seibel
Details:

Cherokee 180

Picked up from shop. Flew great. Flew 10 minutes to home base.

Sat on the ground for 30 minutes. Went to take off. Run up was fine. On takeoff roll had lack of acceleration. Looked at tach and it was at only 2100 rpm. Aborted takeoff. Did another run up and all OK. Static RPM in 23-2400 range. Next takeoff attempt went well.

Flew one hour and stopped for fuel. On the ground for 15 minutes. Takeoff went fine. Flew another hour. Stayed on the ground overnight.

Went to take off. Run up was fine. This time my wife had her eyes glued to the tach. Takeoff roll began with good initial rpm up in the 23 to 2400 rpm range. About 2 to 300 feet down the runway rpm dropped to 2100. Aborted takeoff and tried again. This time takeoff went fine. Flew two hours home with no problem.

Any ideas?

Thanks,
 
Take it back to the shop and tell them to fix whatever they broke. :)
 
Symptom would be about the same as switching from both mags to one mag. Not saying that is what it is, just that it would act about like that.
 
Sounds like an intermittently-working mag.
 
Graueradler said:
Symptom would be about the same as switching from both mags to one mag. Not saying that is what it is, just that it would act about like that.
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My first thought too. Well, not my first thought, but the conclusion I'm coming to.
 
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I would not take off if you had an intermittently working mag. It sounds like the shop just missed this, or perhaps the bad mag was aggravated somehow by clean/new plugs.

It sounds like the shop is only a 10min flight from your home base. Might ask them to drive to your field and have a look at it.
 
It could also be an intermittent induction air leak. An engine analyzer if you had one would help isolate the problem. Either way, it needs fixing.
 
Why don't you make a quick check that your P-Leads to the mags are in good condition and not chaffing or shorting anywhere. Remember, those wires don't power the mag, they ground the mag, anyplace the wire is touching something is a possible spot. Then there is the Bendix key switch issue, they go bad and cause various fun effect that are often transient at the beginning.
 
to me it sounds like a bad ignition switch.
 
Henning said:
Why don't you make a quick check that your P-Leads to the mags are in good condition and not chaffing or shorting anywhere. Remember, those wires don't power the mag, they ground the mag, anyplace the wire is touching something is a possible spot. Then there is the Bendix key switch issue, they go bad and cause various fun effect that are often transient at the beginning.
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Found an uninsulated spot on p-lead just inside the braid.
 
JHW said:
Sorry, that won't do at all. Keep looking until you find something more expensive to fix.
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What do you believe it will cost to make and install a "P" lead set?
 
geneseib said:
Found an uninsulated spot on p-lead just inside the braid.
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Ahhh, hopefully that will be the problem, tape it up good and see what happens. Remember when diagnosing, start work at one end of the system to the other and go through it over and over from cheap to expensive.
 
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Tom-D said:
What do you believe it will cost to make and install a "P" lead set?
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about 30 minutes and maybe $3 worth of junk the last time I replaces one using stuff scrounged from my shelves
 
Because if it worked when the plane went into the mechanic's shop and didn't work after it came out, the aircraft insurance agent probably didn't cause the problem.

Tom-D said:
Why is always the A&P's fault?
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wabower said:
Because if it worked when the plane went into the mechanic's shop and didn't work after it came out, the aircraft insurance agent probably didn't cause the problem.
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Couple of other interesting possibilities are coincidental failure and fraud. The thing that really sucks is when someone brings in the worst maintained stuff with 50 year old baked wires and hoses so old they are brittle and ask me to 'just replace this one thing' in the middle of it, normally I turn those jobs away because I know the minute I stick my hand in there, everything is going to hell and I'm gonna end up eating the rewire job, f-that. You shoulda seen the boxes of garbage wiring and old avionics gear they pulled out of my plane when I had the panel done.:eek: I told them to get all that crap out and I gained 200lbs of useful load.
 
Henning said:
Couple of other interesting possibilities are coincidental failure and fraud. The thing that really sucks is when someone brings in the worst maintained stuff with 50 year old baked wires and hoses so old they are brittle and ask me to 'just replace this one thing' in the middle of it, normally I turn those jobs away because I know the minute I stick my hand in there, everything is going to hell and I'm gonna end up eating the rewire job, f-that. You shoulda seen the boxes of garbage wiring and old avionics gear they pulled out of my plane when I had the panel done.:eek: I told them to get all that crap out and I gained 200lbs of useful load.
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This is why I tell people to expect their first avionics shop visit with a plane to cost about double what it should.

We gained 65 lbs useful load from the Aspen install. It'll only get better.
 
Assumes facts not in evidence. Stuff breaks in the shop for numerous reasons, including incidental contact. "But we didn't even work on the tail strobe" doesn't mean the mechanic replacing the ELT battery didn't move the wire out of the way and indavertantly break one of the few remaining strands that were intact after 30 years exposure to the damp air emerging from the pressurization outflow valve.

Henning said:
Couple of other interesting possibilities are coincidental failure and fraud. The thing that really sucks is when someone brings in the worst maintained stuff with 50 year old baked wires and hoses so old they are brittle and ask me to 'just replace this one thing' in the middle of it, normally I turn those jobs away because I know the minute I stick my hand in there, everything is going to hell and I'm gonna end up eating the rewire job, f-that. You shoulda seen the boxes of garbage wiring and old avionics gear they pulled out of my plane when I had the panel done.:eek: I told them to get all that crap out and I gained 200lbs of useful load.
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wabower said:
Assumes facts not in evidence. Stuff breaks in the shop for numerous reasons, including incidental contact. "But we didn't even work on the tail strobe" doesn't mean the mechanic replacing the ELT battery didn't move the wire out of the way and indavertantly break one of the few remaining strands that were intact after 30 years exposure to the damp air emerging from the pressurization outflow valve.
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:confused: Where did I assume anything? I was just adding possibilities of why things fail when you go to the mechanic, and as far as fraud, I've seen that work both ways where the customer is trying to get extra issues fixed. There was one guy with a 210 at LGB who was so notorious for it nobody in SoCal would work on his plane.

Most of our planes are old, past the service life of the componentry, especially wiring. If your wiring is more than 30 years old, very likely it should be rewired due to the condition of the insulation and terminal connections.
 
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Maybe it should be, but if you're making book you better bet that the same stuff is there that left the factory. If it ain't broke, don't fix it, right?

Owner scams are usually laughably amateurish. A guy recently forgot the gear on his high-wing retrac. A shop jacked it up at the jack-points and pumped the gear down and towed it to his hangar. The shop later got a bill for $10k from the owner's insurance company for "damages during recovery" because the owner told them that the shop used a sling around the tail to lift the plane.

Fortunately, the airport authority was on site and took numerous pictures throughout the process that eliminated any doubt. The tail damage was apparent in the pictures taken before the recovery started.


Henning said:
:confused: Where did I assume anything? I was just adding possibilities of why things fail when you go to the mechanic, and as far as fraud, I've seen that work both ways where the customer is trying to get extra issues fixed. There was one guy with a 210 at LGB who was so notorious for it nobody in SoCal would work on his plane.

Most of our planes are old, past the service life of the componentry, especially wiring. If your wiring is more than 30 years old, very likely it should be rewired due to the condition of the insulation and terminal connections.
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That's why it's worth spending the extra money on the repairs the avionics shop will do your first visit.
 
wabower said:
Maybe it should be, but if you're making book you better bet that the same stuff is there that left the factory. If it ain't broke, don't fix it, right?
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That is right enough that it raises significant quandaries sometimes. With something's it's cut and dried, things like wiring though, it often becomes a tough call. Typically if equipment has three wiring related failures within a year/100hours I recommend rewiring, because that seems to be the point where the system failures will start cascading and is more beneficial in time and long term cost to just bite the bullet and rewire and be done with it for another 30 years, probably longer now with the modern insulator materials. Rarely are wiring problems fatal, but they can be a real PITA and cost a lot of aggravation and delays/missed flights. There are some wires there though that depending on the mode of failure have you dealing with an in flight fire complete with melting, burning stuff fall in your legs, not exactly a pleasant experience with more than one NTSB report with a Fatal mark mentioning it.

Materials have life limits when you exceed those limits you begin gambling, sometimes you win, sometimes you lose. What you need to determine is what the bet will cost if you lose and if you like the odds well enough to play.
 
Not sure that's the way to go. Most of the fleet is in that age range. I'd argue that over an ownership cycle, wiring problems are far less costly and no more time-consuming to repair on a "when-needed" needed rather than shot-gun when something new is installed. Nor does a re-wire necessarily mean all the problems go away. Even with good installs, bad pins, crimps, mis-wires, faulty grounds and many other problems haunt the owners for extended periods of time.

I see it every day and have come to accept it as one of the joys of ownership.

Ted DuPuis said:
That's why it's worth spending the extra money on the repairs the avionics shop will do your first visit.
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wabower said:
Not sure that's the way to go. Most of the fleet is in that age range. I'd argue that over an ownership cycle, wiring problems are far less costly and no more time-consuming to repair on a "when-needed" needed rather than shot-gun when something new is installed. Nor does a re-wire necessarily mean all the problems go away. Even with good installs, bad pins, crimps, mis-wires, faulty grounds and many other problems haunt the owners for extended periods of time.

I see it every day and have come to accept it as one of the joys of ownership.
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Yep, it's a gamble that can go either way, luckily it's not a fixed odds game and you can gain advantage by playing with the correct house and dealer.
 
wabower said:
Not sure that's the way to go. Most of the fleet is in that age range. I'd argue that over an ownership cycle, wiring problems are far less costly and no more time-consuming to repair on a "when-needed" needed rather than shot-gun when something new is installed. Nor does a re-wire necessarily mean all the problems go away. Even with good installs, bad pins, crimps, mis-wires, faulty grounds and many other problems haunt the owners for extended periods of time.

I see it every day and have come to accept it as one of the joys of ownership.
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I think you will find most of the wiring discrepancies happen after some one messed with it, old or new.
 
Agreed, but "messing with" has many connotations. If the back of your wrist inadvertently moves an unsecured wire a couple of inches while you are removing an ELT in the tail-cone, did you mess with it?

Tom-D said:
I think you will find most of the wiring discrepancies happen after some one messed with it, old or new.
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Tom-D said:
I think you will find most of the wiring discrepancies happen after some one messed with it, old or new.
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Yep, you tend to find it more with old wiring as everything gets brittle. The wiring is so dense behind most panels, it's impossible to repair something there without stressing some wiring connections.
 
wabower said:
Not sure that's the way to go. Most of the fleet is in that age range. I'd argue that over an ownership cycle, wiring problems are far less costly and no more time-consuming to repair on a "when-needed" needed rather than shot-gun when something new is installed. Nor does a re-wire necessarily mean all the problems go away. Even with good installs, bad pins, crimps, mis-wires, faulty grounds and many other problems haunt the owners for extended periods of time.

I see it every day and have come to accept it as one of the joys of ownership.
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I should have clarified that with "typically recommend." Obviously it depends on the specific plane, how you use it, and also what the specifics of your situation are.

For me, I've never been based at a field with an avionics shop. While my MX is done on-field and it's pretty simple for me to call up the guys and say "Hey, that old spark plug on the #3 cylinder left engine is fouled, let's replace it", any electrical/avionics failure requires me to fly the plane elsewhere, arrange for a ride home, and then reverse the process when it's time for the pickup. That adds significantly to the cost of a visit.

Since I buy old planes into the second half of their useful life, too, they typically have some hidden avionics problems caused by years of neglect or bad work. When I take it in for an upgrade (because it also doesn't have the panel my heart desires), that first visit makes sense to do it once and do it right. What I will say is I've never needed to take a plane back for a redo for avionics work. It's important to me that these things work given the type of flying I do. This was reinforced after the Aztec's electrical system shut off entirely on me during a dog flight early on in my ownership. For a leisure/VFR-only plane, I wouldn't care that much.

One Navajo I used to fly had a lot of random quirks that I believe weren't fixed properly because the owner (an A&P) could do a temporary fix. Intercoms were intermittant, HSI slaving stopped working now and then, autopilot would randomly become suicidal, etc. I was always afraid that plane would lose all of its avionics on me on an approach to mins at home (which had terrain).
 
Tom-D said:
Why is always the A&P's fault?
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When you go to pick up the plane and as soon as you turn on the fuel pump, fuel starts running out the bottom of the cowling, it's the A&Ps fault.

When the engine starts missing on the first flight and you find two spark plug wires completely loose, it's the A&Ps fault.

When there's a puddle of fuel under the plane the next morning because the sump is not seated properly, it's the A&Ps fault.

Other times maybe not so much. ;)
 
You've seen our shop. Of the 11 techs, three have strong avionics experience, so we probably have a leg up on those who aren't as handy with a wiring diagram and a meter. And they are twin Cessna specialists. And we have warm winters and no state income tax or property tax on personal planes. Say again why you don't live here?

Ted DuPuis said:
I should have clarified that with "typically recommend." Obviously it depends on the specific plane, how you use it, and also what the specifics of your situation are.

For me, I've never been based at a field with an avionics shop. While my MX is done on-field and it's pretty simple for me to call up the guys and say "Hey, that old spark plug on the #3 cylinder left engine is fouled, let's replace it", any electrical/avionics failure requires me to fly the plane elsewhere, arrange for a ride home, and then reverse the process when it's time for the pickup. That adds significantly to the cost of a visit.

Since I buy old planes into the second half of their useful life, too, they typically have some hidden avionics problems caused by years of neglect or bad work. When I take it in for an upgrade (because it also doesn't have the panel my heart desires), that first visit makes sense to do it once and do it right. What I will say is I've never needed to take a plane back for a redo for avionics work. It's important to me that these things work given the type of flying I do. This was reinforced after the Aztec's electrical system shut off entirely on me during a dog flight early on in my ownership. For a leisure/VFR-only plane, I wouldn't care that much.

One Navajo I used to fly had a lot of random quirks that I believe weren't fixed properly because the owner (an A&P) could do a temporary fix. Intercoms were intermittant, HSI slaving stopped working now and then, autopilot would randomly become suicidal, etc. I was always afraid that plane would lose all of its avionics on me on an approach to mins at home (which had terrain).
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wabower said:
You've seen our shop. Of the 11 techs, three have strong avionics experience, so we probably have a leg up on those who aren't as handy with a wiring diagram and a meter. And they are twin Cessna specialists. And we have warm winters and no state income tax or property tax on personal planes. Say again why you don't live here?
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I often ask myself the same question. Probably mostly because I'm a slow learner and haven't found a reasonable employment option. Looking for a business partner?

Your shop is a great example of an ideal repair facility. Although the lowly 310 would feel small and inadequate next to all the pressurized big twins. If I had a base where we had avionics and maintenance specialties even on the same field (much less in the same building), it would be a much different story. I'd also be happy, given that we have more avionics upgrades in the plans.
 
Have your mechanic look up the tailpipe of the mufflers with a good light. The inner liner tube on the Cherokees has a habit of breaking loose and covering the tailpipe opening, restricting RPM due to restricted exhaust. I've seen this before in the Pipers that causes your exact problem. Replacing mufflers should fix it. It isn't the mags or carb.
 
Everskyward said:
No mention of your summers? :D
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Pay attention, dammit, we're talking about Winters.

But to your question, summers are even warmer. July-Aug are downright balmy around 2-3 am, when temps and humidity both plunge to mid-80's and west-Nile mosquitos are no longer hungry.
 
M2mala said:
Have your mechanic look up the tailpipe of the mufflers with a good light. The inner liner tube on the Cherokees has a habit of breaking loose and covering the tailpipe opening, restricting RPM due to restricted exhaust. I've seen this before in the Pipers that causes your exact problem. Replacing mufflers should fix it. It isn't the mags or carb.
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You could actually have them comply with the AD.
 
M2mala said:
Did the muffler prove to be the problem?
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Muffler was OK. As I mentioned in an earlier post, there was some insulation missing on a P-Lead inside the ground braid. Was probably situated where acceleration caused them to short. No problems on takeoffs today.
 
geneseib said:
Muffler was OK. As I mentioned in an earlier post, there was some insulation missing on a P-Lead inside the ground braid. Was probably situated where acceleration caused them to short. No problems on takeoffs today.
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Good deal.
 
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