Ed Haywood
En-Route
OK, but is it a "change to the basic design"?
Shade tree mechanic strikes again
- Thread starter Ed Haywood
- Start date
OK, but is it a "change to the basic design"?
Well most mechanics don’t keep cameras in their tool boxes. So perhaps you just need to get out more. Most guidance prohibits the use of standard tie-down staps/cable ties anywhere out of interior locations. Same with in areas exposed to more than 248 deg F and in areas classified as SWAMP (severe wind and moisture-prone).
True. But they are special approved cable ties (usually blue or purple) and are used to stow extra lengths of subcomponent harnesses and not used as primary support of cables or wires. Adel clamps are used.
Not quite. A properly installed Adel clamp will not permit the same intrusion of grit and oil. Plus if the adel is installed in an area where it is exposed to certain contaminants the prevailing guidance is to seal the edges of the clamp rubber.
Exactly. Facts. Can you provide a legit reference that permits the use of cable ties in engine compartments or their use for securing items to aircraft system tubing? None of my references do.
Last edited:
Dan Thomas
Touchdown! Greaser!
- Joined
- Jun 16, 2008
- Messages
- 10,758
- Display Name
Display name:
Dan Thomas
Steve's Gascolators thinks so. They had to go to all the work of getting STC approvals on it. implying that the FAA demanded it.
Pinecone
En-Route
How is it a change the basic design to replace a gascolator with a better one? I could see it being so for adding one or removing it.
Dan Thomas
Touchdown! Greaser!
- Joined
- Jun 16, 2008
- Messages
- 10,758
- Display Name
Display name:
Dan Thomas
How is it that we need an STC to replace the old alternator with a Plane Power alternator? Or an STC to replace a magneto with an E-mag? These are simple switchouts. But the "basic" design refers to the original drawings which specified every component.
Sure, some stuff is PMA'd, but that doesn't guarantee that there won't be cases where it doesn't fit or doesn't work.
I had trouble with a PMA'd starter on a 180. The power terminal was perilously close to the top crosstube on the engine mount. It would have contacted the mount once the engine started flexing its shockmounts. It would damage both starter and mount. I had to use a Lamar starter instead. STC'd. It fit.
Brad W
Pattern Altitude
reminds me of some of the stuff Orville and Wilbur built
I assure you, it is not. I've had to repair a few mounts because of wire tie abrasion.
Daleandee
Final Approach
- Joined
- Mar 4, 2020
- Messages
- 6,314
- Display Name
Display name:
Dale Andee
As I'm certain you are well aware some parts can look identical and yet the difference can be deadly. I was recently watching a video of the crash of Tuninter Flight 1153 that ran out of fuel because the fuel quantity indicator had been replaced with a nearly identical unit (model 2250 vs 2500).
As for the flight it could be argued that the pilot should have caught the error (he departed without a required fueling slip). Yet this maintenance error was a large part of the cost of 16 lives in the sea ...
I still haven’t seen one picture of a mount with the metal worn. That one picture is just the paint missing. If it’s so prominent of a problem you would think there would be pictures of dozens of clear examples to be found. Do what you want as it’s your own plane or license but at the same time you can’t complain about the high cost of annuals or maintenance when there are people condemning airplanes because of plastic zip ties.
Why? In over 40 years of working on aircraft I never took pictures of things I found wrong unless it was specifically requested. Same goes for 1000s of other issues that are not photographed as a part of performing maintenance. You don't want to believe it because there's no photos, fine. Its only your loss not mine. Rock on.
Dan Thomas
Touchdown! Greaser!
- Joined
- Jun 16, 2008
- Messages
- 10,758
- Display Name
Display name:
Dan Thomas
That paint is urethane. Tough stuff, not easily abraded. But that zip tie ate it and was starting on the steel, which would suffer faster.
Good luck in aviation. It is very unforgiving of ignorance and arrogance.
Pinecone
En-Route
That is why a certified A&P needs to determine if the part does work the same
Dan Thomas
Touchdown! Greaser!
- Joined
- Jun 16, 2008
- Messages
- 10,758
- Display Name
Display name:
Dan Thomas
And THAT is often beyond the A&P's ability. Even the big boys get it wrong sometimes.
Example. The Cessnas used a Dukes fuel booster pump. That pumps is no longer available, so Cessna sourced a Weldon pump. It fits, the fittings all line up, and connecting it is easy. But it didn't work. The circuit uses two adjustable power resistors and a dual panel switch, to get three pump speeds for several reasons. If the engine-driven pump fails, the boost pump is turned on. There's a microswitch on the throttle mechanism on the fuel servo on the engine; at lower power settings the pump's current passes through both resistors, in series. As the throttle is opened to about 15" MP, that switch shorts one of the resistors and the pump gets more juice and speeds up, to keep up with the higher fuel demand. The other side of the duel panel switch shorts the second resistor, giving full boost for priming or for purging the air from the system after the engine runs a tank dry.
Simple? No. That Weldon pumps uses much less amperage to produce the same pressures and volumes. We could not get the resistors adjusted to get the requisite pressures on all settings. The pump wouldn't slow down enough. The lower current draw resulted in a smaller voltage drop across those resistors, so the pump got too much voltage and overpressured stuff. That could be fatal in flight. I worked it all out and asked Cessna for the right resistors, got them and put them in and adjusted everything. They should have issued an SB on it. Never saw one.
How many A&Ps check the pressures after pump replacement, and how many would know why things were haywire>?
Daleandee
Final Approach
- Joined
- Mar 4, 2020
- Messages
- 6,314
- Display Name
Display name:
Dale Andee
The installer was one of the ones found guilty as to the cause of the crash. Yet I'm certain that they did not install a part that they thought was going to cause the loss of 16 lives. Humans are not perfect and we all mistakes, sometimes they are deadly ones.
The fuel quantity totalizers were identical except for the model number which itself was very close to the same. Seems that after the crash they made a change so that the two similar models wouldn't be easily confused ...
Pinecone
En-Route
Well, if you are replacing it with a different pump, I would hope that any A&P would test the pressures.
I did not say that every swap will work, just that some (not all) are not a redesign of the fuel system. Your example is, because the pump has several speeds that are controlled by new switches.
Although, I am not sure why you needed the different speeds if the original pump was single speed/output. Figure out the resistance needed to get the proper pump output and leave set to that one setting like the original pump.
Doc Holliday
En-Route
We have these shade tree mechanics because of the demand. There are still lots of owners who prefer to buy a signature at a discount rather than properly maintain the airplane. The FAA exacerbated the situation by making the Inspection Authorization easy and available to anyone with an A&P.
Dan Thomas
Touchdown! Greaser!
- Joined
- Jun 16, 2008
- Messages
- 10,758
- Display Name
Display name:
Dan Thomas
So you don't understand the Continental fuel injection system. There are no "new switches." The system has a positive-displacement engine-driven pump that moves more fuel as the engine RPM increases. That pump is part of the whole fuel metering design. When it fails, and you activate the booster, that booster had better be delivering a fuel pressure close to what the servo can handle. Otherwise it will flood the engine and kill it. So the switches and resistors do that. Installing a new pump that has a difference performance curve wrecks the calibration.
The Lycoming/RSA fuel injection system doesn't need a multi-speed booster pump. It has regulators in the fuel servo that take care of the pressures. Different concept entirely.
schmookeeg
En-Route
I thought it was a suspiciously easy path too. What did IA entail before it was just an exam?
The sad thing is, It’s only going to get worse as these aircraft continue to age and start requiring real work that owners will refuse to pay for because they think the mechanics are robbing them.
Dan Thomas
Touchdown! Greaser!
- Joined
- Jun 16, 2008
- Messages
- 10,758
- Display Name
Display name:
Dan Thomas
I got that frequently already. It's especially bad when the owner can barely afford to buy it, gets a cheap airplane, then thinks that because it's a cheap airplane the labor and parts should be cheap, too.
There really is no such thing as a cheap old airplane. Unless it was a well-maintained and cared-for machine that your uncle left to you in his will, and even then it will cost you to insure it and feed it and maintain it.
Shop rates are pretty much the same for an old Chevy compact as for a new Peterbilt.
Also seen my share of horrors.
My take is a lot of owners are actually pretty much in the dark as far as the
maintenance aspect.
Maybe we need a “ Aircraft Owners License” ?
They are responsible for maintenance and since they fly over the public maybe something is needed ?
My take is a lot of owners are actually pretty much in the dark as far as the
maintenance aspect.
Maybe we need a “ Aircraft Owners License” ?
They are responsible for maintenance and since they fly over the public maybe something is needed ?
Doc Holliday
En-Route
Already have it.
91.403 General.
(a) The owner or operator of an aircraft is primarily responsible for maintaining that aircraft in an airworthy condition, including compliance with part 39 of this chapter.
Dan Thomas
Touchdown! Greaser!
- Joined
- Jun 16, 2008
- Messages
- 10,758
- Display Name
Display name:
Dan Thomas
If the flight student gets anything about ownership in his groundschool, it's pretty minimal. Most owners don't seem to know that airworthiness is their responsibility. They figure that they're paying the mechanic to keep it airworthy. But when the FAA issues ADs, or the manufacturer issues SBs, they go to the registered owner. A good mechanic will check the AD biweeklies to see what's new, and will have a subscription to SB services for the airplanes he maintains.
Our commercial ground training included my Aircraft Systems course, and we spent a whole session on this stuff.
In general, it was an interview, then a written/oral/practical test of whatever proportions the ASI determined. You supplied your test materials like AD listings, etc. In the end, the ASI determined if you got an IA, not a test score. Usually a number of applicants had problems making it through the interview.
Always been a believer aircraft ownership should be part of any pilot certificate training. It wouldn't need to be anything fancy and could simply follow the Plane Sense AC. Also to take it one step further, 91.403 should require a yearly written logbook statement by the owner that the aircraft meets the terms and conditions of Block 6 on the AWC. I think of it as putting an open season on hangar fairies and $200 annuals.
Last edited:
Doc Holliday
En-Route
Like anything else, a bit of self education goes a long way. Ignorance of the law is not an excuse.
Ah; Bell brings the memories sailing back!
I was at Bergstrom AFB ( Austin TX) filing the nicks out of a Cherokee prop.
A tap on my shoulder and I was talking with a fed from San Antonio. Ultimately the discussion turned to me getting the IA. He said he could see I was “ actively engaged “ and said to stop down to see him and take the test.
I was unaware of IA Test Prep books in that era. Another factor was you had to bring ALL of your test materials as Bell related. This was an issue as you had to BE an IA in order to get the free paper ADs. Fortunately I met someone that I am forever grateful to; Percy Casey. He was retiring and said I could use his materials but a LOT of revisions had to be updated. This turned out to be a real blessing to
me because after doing the revisions I could find the information quite readily. This is something many folks take for granted. Two trips to the car to bring it all in though.
The first section was “ Closed Book” on Part 65; primarily IA privileges and limitations. The other 2 sections were “ Open Book” on Annuals, Major Repairs and Alterations. They were essay questions and not easy. One question I still recall was; “ Describe How you would inspect the landing gear of the aircraft you selected?”. I wrote and wrote and wrote some more. Even copied part of the Cherokee Manual. I got it wrong. The ONLY answer they would accept is “ In accordance with the manufacturers Service Manual . The sweat was rolling!
While 70 was the supposedly minimum passing grade, the correction process was very subjective. The key was being able to find a reference to justify your answer. This is where all the hours spent revising paid off well. Just about every other question turned into an oral exam.
To this day I would say it was the toughest exam I have ever taken.
I was at Bergstrom AFB ( Austin TX) filing the nicks out of a Cherokee prop.
A tap on my shoulder and I was talking with a fed from San Antonio. Ultimately the discussion turned to me getting the IA. He said he could see I was “ actively engaged “ and said to stop down to see him and take the test.
I was unaware of IA Test Prep books in that era. Another factor was you had to bring ALL of your test materials as Bell related. This was an issue as you had to BE an IA in order to get the free paper ADs. Fortunately I met someone that I am forever grateful to; Percy Casey. He was retiring and said I could use his materials but a LOT of revisions had to be updated. This turned out to be a real blessing to
me because after doing the revisions I could find the information quite readily. This is something many folks take for granted. Two trips to the car to bring it all in though.
The first section was “ Closed Book” on Part 65; primarily IA privileges and limitations. The other 2 sections were “ Open Book” on Annuals, Major Repairs and Alterations. They were essay questions and not easy. One question I still recall was; “ Describe How you would inspect the landing gear of the aircraft you selected?”. I wrote and wrote and wrote some more. Even copied part of the Cherokee Manual. I got it wrong. The ONLY answer they would accept is “ In accordance with the manufacturers Service Manual . The sweat was rolling!
While 70 was the supposedly minimum passing grade, the correction process was very subjective. The key was being able to find a reference to justify your answer. This is where all the hours spent revising paid off well. Just about every other question turned into an oral exam.
To this day I would say it was the toughest exam I have ever taken.
Doc Holliday
En-Route
A large number of IA's today would never make it through the old test. IMO the FAA dropped the ball on allowing anyone to take a multiple choice test and be rewarded an IA. The shade trees came out in force to get the IA and offer signatures for sale.
Checkout_my_Six
Touchdown! Greaser!
Shade trees....unite.
We see the effects of all the recent shade trees....planes are falling from the skies.
We see the effects of all the recent shade trees....planes are falling from the skies.
schmookeeg
En-Route
unite to form... liability singularity!
(puts on supershadetree ring)
==
That ASI interview-test-chump-stump sounds subjective and arbitrary as hell.
(puts on supershadetree ring)
==
That ASI interview-test-chump-stump sounds subjective and arbitrary as hell.
Having changed an engine in a 1969 Bonneville using a chain hoist hanging from a [shade] tree limb, I think I can qualify...
Dan Thomas
Touchdown! Greaser!
- Joined
- Jun 16, 2008
- Messages
- 10,758
- Display Name
Display name:
Dan Thomas
Sometimes they do, but some failures aren't reported. The airplane lands safely and nothing more is heard.We see the effects of all the recent shade trees....planes are falling from the skies.
Stuff tends to accumulate. A cheap annual, year after year, misses cracks and corrosion developing, misses wiring being chafed, misses worn seats and rails, misses cracked exhaust parts, and with each miss the chances of an accident go up. Get enough defects and one of them will bite you. At the very least, a prebuy when you go to sell the airplane will find a raft of this stuff and nobody will want that airplane.
I fully expect that we'll someday start seeing more failures as corrosion, fatigue and age take their toll on old airframes.
Zeldman
Touchdown! Greaser!
I have seen some aircraft pilot/owners working on their airplanes in Alaska and I am not sure if they ever had a student pilot certificate or even a sign off to solo...
If you were on your game, you made it through. If you only thought you knew what you were doing, you didn't get past the interview. Kept the riffraff out and all and all created a basic knowledge level across the IA ranks. Once the test changed and IAs became a dime a dozen, it created more problems than the FAA anticipated.
bluerooster
Pattern Altitude
- Joined
- Nov 28, 2011
- Messages
- 2,072
- Display Name
Display name:
shorty
Back to the Adel clamp vs Zip tie; The zip tie is about a 1/4" wide, and the adel is about 1/2"-5/8" wide. Therefore the adel covers more area, and when tightened properly is less likely to be vibrated around, than the zip tie. After all a length of rib lacing cord will effectively saw off a piece of 4" sch 40 PVC pipe in short order, while a nylon strap will not. same principle applies to zip tie vs adel clamp.