Comments On Removing/replacing Instrument Clusters

GMAs · #1 09-11-02, 03:27 PM

Ahhh... well... I was reading thru the description of work accomplished... that was posted by 2362s... and after someone made a comment I have to agree with them... something is not right for all...

First they commented about the weight and how to weight the system... here they are right.. you pull the plug on the old guages and weight them its not the same as when he describes all the wiring and pigtails for the new system... so his 5.2 lbs may in fact be correct for that installation but, the removal of the old was never done right... as it to has wires and connectors... so the removal of 2 and adding of 5.2 is in question...

Next came the removal of the oil pressure lines... and here we have a delima.... I too prefer the mechanical guage because of two reasons... first redundency... if the electrical system goes out.. the engines keep runing but, the oil pressure goes by..by... how do you know when its hitting the bottom.. if the electrical system went some time earlier... and when it went so did the guages... and second... the mechanical gauges are more prone to respond much quicker than the electric ones... I don't think new technology has progressed that far that they are as quick as the old mechanical ones...

So in this area... I would pefer the older mechanical guages...

and under item No. 6... most of the 73 on do not have this in them... it would be nice but, not necessary... so cessna took it out... just like the fire light for the rear engine... it is nice to have but, not necessary unless you need it...

Now for the people who want it... ya it can be added to the system... but, it will require some splicing into the existing system and then going to and from the device... I did see a neat installation on one skymaster where the guy had digital readouts... and he put his shunts up on the firewall to one side of the regulator diodes... it was a good nice looking cheep installation... but, again do we need it... nope... I would think a simple volt meter along with the amp guage is all one would need to check his system....

Actually I think someone will eventually come out with a computer system monitoring device... where if things change.. it will show you on a screen... no more oil pressure, fuel flow, temp guages... it will note any changes and let you know... like the new 777 has... that way you have time to do other things ... like kill the duck for getting you into the clouds... and seeing if the old dog really does fly.. by itself... for looking like he would bite you... smile...

And the fuel quantity sending units are different on the later models.. with the pennycap system... than the early ones... I perfer the early ones because they have less trouble.. but, the pennycap when working right is pretty accurate and better... but, that is when they are working right... most I don't think doe... anymore... and the older systems keep on ... keeping on... smile...

and finally the item no 19... this does not fall under the normal socope and guidelines of the cessna 100 hr and annual inspection... it can be done concorently but, under the guidelines.. nope.. this is a remove and replace with type thing... and as such.. the reason why your putting it on a 337 form... for field approval...

Once it is installed... you are then supposed to have a section in the POH that describes its operation and function... and at each annual it WILL be inspected as part of the plane... like your instruments are currently at annual... the I especially liked the part ... that is on this paragraph is the ... new gauges require no additional.... maintaince... well here I would say that the instruments need calibration and certification every so often so they do need maintance... everything on the plane does... smile...

... and .. I would change the latter to... Any needed part numbers and/or troubleshooting references, which are a part of this field approval... will remain with the... ya ya... that is what the log book entry is for... the POH has the operation part... the maintance manual has the other stuff... so its Maintance records... not aircraft permanent records... kinda thing... note we only have two things that tell us how to operate our plane... the maintance and the opreations manuals... the latter being the Pilot operating handbook... now do you put the stuff in their... well the operation part... but, the maintance stuff is broken down into to areas... the log book and the maintance manual... the log book says what you did and when.. the maintance manual is what you are refered to... to do the maintance correctly... right!!!....

Test results are of no interest here... and the results that are supplied with/by Mitchell are PARTS... you by installing them in your plane and filling out the 337 form are RE-ENGINEERING to make his part fit where a old one was removed and YOU REPLACED IT WITH HIS..... Like GE made the light bulbs.. and now Cessna does... its similar but, it has a different part no... so its has a PMA or FAA approval number on it.. (they went and said.. hey we make the same thing... to the same specs.. but, its a LITTLE different so we are not infringing on their rights... and the FAA give it a approval no... after they test it...) same here...

And finally the last item... NO 20.... YA.. Ya.. again we keep seeing this statement by A&P's and IAs.. who are not with the program... here look lets go through it agan...

WE take a product..(Widgett)... its Type certificated... to go into our plane... (STC'd)... Ok.. it will work... or will it...

Some time ago we put a whiz bang in... and that had a STC also... it is placed right next to the new Product that we are going to put in now from Widgett.... but, did Whiz bang know we have a Widgett installed .. nope they only got their certification for a stock airplane... from the factory... so theirs will work... so will Widgett.. but, will they work togeather... nope... they interfer with each other... who is to blame.. the FAA, the manufacture, the owner... the mechanic... well no one... its a grey area that is not really covered... and so you give the Widgett to the mechanic and say... install... he does what you said.. but, how is he to know that the widgett and whiz bang don't get along... he doesn't fly the plane... and after all it did fit in.. somewhre...

So he goes out and runs the engine and says... its ready to go.. both come on and light up... and seem to function indivadually by themselves... but, is the plane airworthy... even with all systems operational... and he writes in the log book ... All systems functioned normally.... did he take the plane up and fly it... did he ask the manufacture... hey will this work with the other system installed also... nope.. he just said.. ran the engines and everything appeared to function correctly and normally... but, things are not right in mudsville...

So what we are asking.. and the FAA ... is that you do a compatabliity test... starting with asking the manufacture... will your product interfer with any of the other systems on the plane... and list them... letters are good... phone calls are nice... E mails are... not legal...

Most of the manufactures will know about problems that other systems have in their operation... will they do anything to correct the problems other than blame the other guy... well in the case of King radio.. and IIMorrow and their GPS's both seemed to know about the interfearance of the units.. King said ours it TSO'd and therefore its OK... IIMorrow said.. ours is TSO's and therefore its OK.. but, put the two of them togeather.. and they are not... the radio when transmitted would disrupt the GPS... so IIMOrrow gave you some attenuator pads to keep it from happening... but, King radio says ..you do that and you don't meet the specs that we certified to the FAA... and FCC for reception and range... nice huh.. your out flying in clouds and things are just ducky... till you hit that hill... because your on the frequency that disrupts the GPS.... yep and guess what its sill is... with other radios.. including kings own... so the location of the GPS antenna is real important... so is the ADF, DME and Transponder... all of which are on airplanes.. but, the DME will talk to the transponder and vice versa.. if install individually... and no consern about compatability is mentione... to the manufacture.. who will immediately say something like.. well if you use them two... you want the antennas about yea far away from each other... the further the better... but, the mechanic says.. Hey we can't hook the trailer on the tail of this beast.. so where do I put it... and they make the recomendation...

So what should have been said here is... installation was completed as per manufactures recomendations with existing systems on board. System was inspected tested and found to be COMPATABLE with other systems in the aircraft.... if you want to add you took it out and flew it and did a systems check, engine check and the rest.. its up to you... but, the key word here is COMPATABLE and doesn't interfer with other systems already installed at that date...on that plane... The wording " All systems functioned normally.... is another one that we don't like to see... instead it should be all systems functioned per manufacturs specifications in normal ranges... why because cessna didn't build the widgett... or whiz bang... they built the pane.. and the other MANUFACTURES built the other stuff.. so we have more than one MANUFACTURE... on this plane now... thus the MANUFACTURS' instead of manufacture.... smile...

YOu have to do this to maintain another word... that is coming into play... contenued airworthyness.... but, we won't get into that right now... my fingers are tired of typing and its lunch time.. smile... GMAs...

stackj · #2 09-11-02, 10:52 PM

GMAS - This reply is to address some of your concerns relative to the Engine Gauge Cluster for 2362S

Weight and balance issues - I did not account for the oil pressure lines I removed or the terminal lugs I cut off the end of the old wiring. The Pigtails were included in the weight of the new gauge cluster. I soldered the pigtails to the existing aircraft wiring and added a couple of wires for the oil pressure gauges. I also put heat shrink over the soldered connections. I think those small differences in weight are negligable.

I agree with you. The old Bordon tube oil pressure gauges sure have an advantage when the entire electrical system goes south. I have had that happen, but it was a shutdown choice when a fuel quantity indicator decided to turn into smoke. This version also has an advantage in that there is no longer risk of an oil leak causing problems in the cabin. I don't see any difference in the response time of the Bordon tubes versus the electric guage. Could be a wash... I'd say a matter of choice. Adding the electrics here does add another opportunity for failure.

Item number 6 - I have been instructing a friend in a 71 (I think) Skymaster. I was surprised to note that he did not have an ammeter. There were only idiot lights for the electrical system. I am much more satisfied with the meters. I would think it would be up to the aircraft owner to determine whether he (or she) wanted to do multiple meters or keep just one meter and the rotary switch.

As you noted, this system will only be useful on older aircraft. The newer ones do, in fact, have a totally different fuel quantity system. Unfortunately, this gauge system does not improve the accuracy over the original system. It just gets rid of the smoke when the gauge decides to go South - no matter which way you are flying.

I think this cluster really only opens some options for solving some problems. In my case, I could have gotten a four gauge cluster and just replaced the fuel gauges. I just didn't want to have to hang them some place else on the panel. Also, I can replace individual guages now and don't have to pull the whole panel to get a single gauge repaired. You can even operate the airplane with some of them removed --so long as you placard the removal.

As for items 19 and 20... Boy! Is this ever an area of ambiguity! This strictly has to be worded in such a manner as to please the person who will approve the change.

I expected to do a technical write-up and go with that, but the truth of the matter is the FEDs desire wording that tends to indicate that all applicable sections of AC43 and FARs are covered. There really isn't much interest in the "how it work's" department.

And, YES, you caught me. I am not an A&P, I'm one of those rare A only's. And I only got that to protect my airplane from so many mechanics to which maintenance is just a daily routine. I make some mistakes, but, so far, I haven't done things so dumb as to hang a propeller with the blades on backwards or install an induction air cable in such a manner as to infringe on the ability to return the landing gear handle to the down position. And most of the time, I don't break somthing else while fixing the original problem. I'm doing this for self protection.

I do appreciate your comments and will consider them when I try to make my next change to the Skymaster. The cowl flaps on this model use the 17 foot long cable to drive the satisfy the position switches when the flaps have reached the chosen position. My shop was able to attach this to the rear firewall by clamping it about three inches below the hardened end of the cable. Guess what happened the first time the cable decided to be a little stiff. Yep, it bent the cable severely enought to render it useless. $250 worth of cable and $1000 worth of labor - SHOT. Anyway, the next job is to replace that assembly with the newer arrangment such as found in the 71 model. I currently have Mr. Nieser looking for parts for me.

I'm sure it will be interesting to get the Form 337 wording just right - again.

Jim

GMAs · #3 09-12-02, 12:11 AM

Jim... no matter how its done... I am sure you have a better plane for it... I agree.. the 60's were great but, the new stuff is much better... and I want to thank you for coming back and letting us know how the new panel is working...

As to the wt and bal... ya I agree.. because we have engines at both ends of the plane.. its not going to make much differance.. and whats a couple of lbs between friends anyway... smile... so I will agree with you on that... however, if it were I... would have pulled complete new wire.. and not spliced in as I have found splices and pulgs are NO. 1 sources of problems later... but, ya do what is necessary to make ends meet.. and splicing is acceptable...

ya the later ones left a lot out that the early ones had because the military specs changed... to civilian...

As to amp meters... and volt meters... you can interchange them.. and still get a picture of the system...

Here is what another person wrote to me on the subject too.. but, didn't put it on the web...

He said that he came off the same place the large diodes are... knowing that the more current their is going thru them the higher the voltage drop... OK... true... this then he put into a couple of digital light bars...(voltmeters) that are calibrated for 0 to 38 amps.. but, because they are not really amp meters per say.. he calls them per cent load meters... ahhhh now thats a twist... what they indicate is how much load they are putting out... in verticle graphic form... then he said he replaced the little amp meter with a digital volt meter.. and a switch that toggles , rear, front, and center is bat.... from that he can tell what the system is doing all the time... neat huh... and best of all he said it cost fractions of what some of the mechanical ones do.... and the electronic stuff is more rugged and sealed chips make it almost bullet proof...

he also put in a part about changing out the pannel lights to LED's and can have different colors by changing the voltage on them... as well as dim them down... some of them have been tested at his UL lab for over 10,000 hrs now.. and keep on going... Can we say good bye to filiment bulbs... I think its coming.... and he has gone one better for the voltage regulators... he came up with a circuit that he is trying out.. that utilizes high speed switching... to sample and then adjust the alternators... right at the source... along with a auto shut down if overloaded or shorted problems occur... he claims he took a long look at the way the auto industry is doing it.. and applied some of the ideas to his new regulators... the rear has remote sensing... so that it will keep up with the front one... as they both sense off the same point... but, have a second sense off the alternator itself... to try and balance them... neat huh... and they auto reset faster than you can get the light to come on... so he says...

As to your work in the wording of the acceptance.. ya its a lot of work to get it right... but, you almost have to be a layer now a days as well as a mechanic... but, I thought you did a good job on the location paragraph and page kinda thing.. that is what most want now a days too... YA Done GOOD HERE...

And never be ashamed of being a Airframe mechanic... I know lots of them who are artist and do better jobs of specializing in just their work than us A&Ps who have to be a jack of all trades kinda person... I tip my hat to you... You are a professional and as such its a honor to discuss things with you...

the FAA inspector who is signing this thing off figures in the works too.. but, I have found that most of them are not as experanced now as some of us are... of course they are a lot younger in age too...and that may have something to do with it... but, never the less.. he is signing his life to your plane.. and his signature is approval for return to service... I have seen some of these bimbos... approve things that they never even looked at... but, their life is on the line so to speak and if they sign... and stamp... hey its theirs...for life... of course they get a little mad at us IA's for not cluing them in... and say were responsible for their actions... I just smile and say.. he who gets paid the big bucks is it... smile... so if he wants micky mouse paw print.. then he gets it... otherwise... we kinda guide them along... sort of ting...

As I have always said.. its not the FAA that keeps planes and pilots safe... its people like you, the mechanics and inspectors... after all we are out their...making decisions and re-engineering the thing... they are in their offices... playing on the computers... and filling out their time cards... kinda thing... but, not to degrade them all... I have a few that I give a run for their money every now and again... and they do the same to me... I even had one that took off his jacket... yep actually rolled up his sleves and fixed his tie out of the way... and got in with both elbows.. and got greasy... holding wrenches and inspection lights as we tore into a engine that came apart for some unknown reason... and can you believe this... he stayed till after 4 and we got to the root of the problem... before he went home... he actually turned out to be a nice guy and good friend ...but, don't tell him that.. or it will make his head swell up... now that is the exception and not the rule.. but, we still argue with each other almost weekly... on the phone too... he is what I call a good FAA person... who wants to know why something is gone wrong... and how to keep pilot and people safe... only problem I have with him is he won't take NO for an answer... as he keeps saying he wants me to join them... what and miss all this fun... never... smile...

good luck on your cowl flap system... ya if I had more time I think I would sit down and come up with a better cheeper system... their has to be a better way than keep busting motors and cables... and the cost is way out of line... but, who is going to take the risk... and who is going to do the work... kinda thing...

thanks for taking the time to reply... and I hope that others will also learn and profit from our conversations... here on the web.. after all that is what its for...

Be looking for your article... you will have to send us all copies.. so we can put it in our files... ahhhh a nother peter Garrison... writer to be... its great to know ya... and you will have to come and show off your work... at one of the upcoming meetings... if I can ever help out... GMAs..

stackj · #4 09-12-02, 06:47 AM

Before I sound sour at the FAA inspector, I just want to say that the person who worked with me on this project was very helpful. The only thing that surprised me was that I expected the justification on the Form 337 to be a detailed technical write-up (probably because I am a techie and have been all my life). The needed language surprised me, but Geez... you're right... you have to be a lawyer to get everything just right so no-one came come back later and sue your integrity away.

It was, in fact, this person who suggested that I complete the remaining requirements to get the A certification. He did this after actually coming to the airplane, reviewing the plan and other work I had done on the plane under the supervision of other A&P/IA's.

I must state that I am much appreciative of his help and support.

Jim