totter

I would not call myself an expert, maybe just qualified to answer questions. I started this thread because there seems to be a lack of understanding, on a whole, as to the maintenance requirements, regs and just plain general knowlodge of maintaining Part 91 aircraft for jumping. I was not asking for opinions, though I shall take them, I was asking for thoughts and qeustions concerning this issue, which these days seem to be on a lot of peoples minds. As to my opinion on jumpship maintenance: There are a few operators that will go to great lengths to properly maintain there aircraft. There are many that do just what is necessary to keep the aircraft airworthy. The dropzone that I was at use to lease an Otter. It was at the DZ all summer, flying 6-7 days a week, putting 10-20 hours a week on the aircraft. It never left the DZ. Mechanics from the lessor never came to the DZ. The season ran for approximately 27 weeks. That works out to 270-540 hours for the season. The inspection interval for an Otter is every 125 hours. Needless to say we stopped leasing.

I am starting this new thread for everyone to voice their thoughts on aircraft maintenance as it pertains to jump aircraft. Many of the posts on "Incidents" end up going out on tangents unrelated to the original incident. For example the Mt. Vernon accident. Yes, the aircraft should not of been flying, but the prior lack of maintenace did not cause the accident. It was the pilot's lack of ability to maintain proper airspeed which led to the stall-spin. Let's stick to that on that post. Here I would like to open up a discussion on the maintenance side of this incident & other concerns about maintnenance. I know my profile is blank, so here is some info on myself. I am an A&P of 15 years with my IA. I worked for numerous years on jump aircraft from 182s to Twin Otters. I was Assistant Director of Maintenance for Seaborne Airlines for a time. They are a 121 operator running Twin Otters on Floats. I am currently Assistant Director of MX/Shop Supervisor for a 135 operator running Turbine Single Otters & Beavers. I am no longer a current skydiver, sold my gear, so I do not have any ties to the jump industry. Hopefully this means that my replies can be unbias and factual. I am more than happy to share my knowlodge with anyone who has a question and also my experiences of running a maintenance shop for jump aircraft.

The big question? Will TK set himself on fire this year with the fireworks? It's a don't miss for anyone who has not been there.

Sorry, my "Y" was not working.

Maybe you should talk to Lyle Presse or Jim Slayton on the matter. The ran the "Go Fast" compition and boogie there for a couple years. I believe that it was 2001 thru 2003. The would be able to shed some light on the difficulties of such an endevor and also why the event is not there anymore.

On a -20 engine there are many linkages that all connect to one another at the front of the engine. This is called the Propeller Reversing Linkage or Beta Linkage. It is all connected to the Power Lever through a wire rope, Cam Box, Rods and cables and pulleyes. When everything is "In Rig" or properly adjusted, the engine and prop will do a certain thing at a given Power Lever setting, i.e. given torque at a given engine speed. Now with all these linkages. Each one has a given angle, dimension or distance that it is required to be at a given power lever setting when rigging the engine. These factors need to be repeatable. Meaning once set you need to be able to move the Power Lever a couple times and reset it, this by the way is full forward, and have those angles, dimensions and distances be exactly the same as they were set. If any of the linkages or bushings and bearings that connect them all are worn, causing slop, then the rigging will not be repeatable. If the linkages that go to the Propeller Governor are worn or "Out of Rig" then this could cause the prop to "Hunt". This means that the prop is trying to stay at its governing speed, but can't, and the blade angles are constantly changing to compensate. This will cause a torque flucuation. If the linkages that go to the Fuel Topping Governor are worn or "Out of Rig" this would cause ALL the engine parameters to flucuate. Those two issues would only effect on take-off until the pilot pulls the props back for climb. Then everything tightens up and is fine. Plain and simple; Yes.

If you would like to get into detail, for a PT6 engine, that the average person will just go HUH!! at then; The First Stage Reduction Ring Gear is allowed to "float" move fore and aft in its housing. There are grooves that aree cut on an angle on the outside of the ring that mate up with grooves in the housing. As the Propeller starts to generate more Torque the First Stage Ring Gear then begins to move. Riding on the forward face of the ring gear is a metering valve. As the ring gear moves aft, the metering valve is allowed to open more and more as the Torque increases. This intern ports more engine oil to the Torque Transmitter. The Torque Transmitter is located on the Right Hand, Forward side of the Reduction Gear Box and is mount directly to a boss. The transmitter has a vent line that runs to a fitting on the opposite side of the gear box. This line carries Case Pressure to the Transmitter. The transmitter then uses a ratio of oil pressure/case pressure and sends an electrical signal to the indicator. The indicator is basically a small AC powered motor. As torque increases, electrical power signal increases, motor spins faster raising the needle. After all that it was much easier to just say what I said.

It's like being head down as compared to belly to earth.

I will try to explain this as easily as possible. Torque is basically the measure of engine power at the prop. The term torque is used because the gauge shows a value of rotational force. Example: 100 series otter. Max take-off torque is 42.5 psi @ 97% Propeller RPM without exceeding 750 degrees T5 temp. What all that means is that the engine will produce maximum power at those figures. For a PT6A-20 that would be 550 horsepower. It is kind of difficult to explain how torque is measured. To make it easy but vague the torque reading is the measure of Engine Oil Pressure as metered through a valve. That Oil Pressure is then picked up by an AC powered Transducer that measures that oil pressure and converts it to an electrical signal. That signal is then sent to a gauge in the cockpit where the pilot reads its value in PSI. Now this explination is for a Twin Otter. In a King Air the system is the same, but the gauge reads in Foot Pounds. In a Caravan or PAC 750 there are no electrically powered transducers. The oil, ubder pressure, is piped right to the gauge. On a -20 Twin Otter there are several things that would affect the proper operation of the Torque Gauge. #1 is engine rigging. Proper engine rigging is critical on a -20 engine for everything to operate properly. Not that it is unsafe if the engine is out of rig, but an out of rig engine will cause torque, Ng (engine speed) & prop RPMs to flucuate. #2 is Oil level in the engine. The amount of oil will effect the "Indication" of torque. Even though the engine is producing the proper torque, the lack of sufficient oil will affect the indication.. #3 is a fault with the indicating system. #4 is an issue with the engine or propeller. If you would like to go into more depth than this I will be more than happy to explain further. Hope this does answer some of your questions.

Chris, I guess I should have been a little less vague in my last post regarding the the above. The FAA may mandate that operators adhere to the engine TBOs, but the also must give the operators the option of maintaining those engine(s) on an APPROVED ON CONDITION PROGRAM. If they, the FAA, were to make it MANDATORY that all skydive operators of turbine aircraft overhaul their engine(s) at TBO then they would be holding jump operators to a HIGHER standard than 135 & 121 operators. 135 & 121 operators are given the option to do either. The key word is APPROVED. I don't think that they will allow operators to just maintain their aircraft any old way anymore. If operators want to run past TBO and be on condition, then they are going to have to have an APPROVED ON CONDITION PROGRAM to do so. Please don't take these as "fighten words" because I do agree with you that there is a huge short coming in the industry that needs to change. I do disagree with this statement, though. It is not a matter of how much TIME SINCE OVERHAUL is on the engine, but what was done in that time to the engine. I work for a 135 operator that runs single engine turbine aircraft. We operate ON CONDITION as part of our GMM. We have one aircraft that has just under 8000 hours since overhaul. That's more than twice the TBO of 3600 hours. It is a strong running engine and I have no issues with myself or my family riding in that aircraft. The difference between us and the typical skydiving operator is the way we maintain it. Fuel Nozzles every 400 hour w/ a borescope inspection. Nightly Turbine Rinses & Comp washes. We do propeller balances and vibration analysis of the engine every 400 hours. We do oil analysis and Trend Monitoring. This is where the changes to Part 91 or 105 will be made.

The FAA can not make it mandatory for Part 91 operators to comply with engine TBOs, unless they were to issue an Airworthiness Directive. And even then it would probable not get through the NPRM hearing. Something like this would effect ALL operators, Part 91-135-121 alike. There are many operators out there the run "ON CONDITION". All would have to comply. Now you have AOPA, NBAA and GAMA lobbiest breathing down the FAA neck. In my opinion the worst that will happen is that the FAA will want skydiving operators to draw up and submit their own ON CONDITION Program for the engines and an Inspection Program for the aircraft. This would be along the lines of Part 135 without making it 135. This way each Owner/Operator is stating that this is the way that our aircraft will be maintained and we will do it this way. Once the FAA approves it that's it. Its not cost prohibitive and each operator can tailor their program to How Much the fly the aircraft.

TK, When you compare skydiving to the rest of General Aviation it is apples and oranges. The accident rate for "other than skydiving" aircraft is higher. There are some other more important differences, though. 1) The accident ratio for skydiving aircraft is higher, at least for this year. If you look at the thousands of "private" aircraft flown to their accident rate and then look at the hundred some odd aircraft used for skydiving and its accident rate, there is a big difference. 2) When Joe Smith takes his 210 out for a Sunday afternoon and balls it up into a tree, killing himself, it does make it to the news. Its just not big news because he did not take unwilling people with him. When 10 skydivers pay for their jump tickets or tandem jumps they are kind of expecting that the aircraft that takes them to altitude is safe. You know the saying, "The jump is free, it's that ride that costs you." They are paying passengers. If the pilot makes a mistake or the aircraft has a mechanical issue and crashes these people are unwilling participants. That is why these events get more media attention. Just like when a MD80 nose dives into the Florida Everglades. As for oversight it depends where the DZ is located. If it's located near a FSDO office then the degree of oversight is much larger then if the DZ is located in the middle of the Great Plains 300 miles from the closest FSDO. Also, with Part 91 General Aviation aircraft, the FAA is not required to make regular visits. The amount of GA airports and aircraft just out weigh their manpower. As far as operators go, it's the ones that believe that they are above the Regs or can "Do what ever they want", that are going to make it hard on the operators that do toe the line, as you do. When you fly your 182 with the Carb heat not working and ball it up short of the runway and during the investigation the FAA finds that maintenance was not being performed by a certified mechanic. What do you expect. When there is an investigation due to an incident and the FAA finds that the pilot is not appropriately rated & their medical is out of date. What do you expect. I did not know Scott personally and I was not familiar with that aircraft or his operation. But Compressor Blades just don't fail. There was no sign of FOD damage, according to the NTSB finding. This leaves distress caused by an Overspeed condition of the compressor section or corrosion of the blades or , I hope not, parts that were past their life limit. The first two of these probables have correction actions that are not difficult and in the beginning, not that expensive. Unfortunatey the third one is harder to correct because the easist way to save a buck is to fudge your aircraft's time and cycles on the records. And unfortunately there are operators that do this. Sorry for the rant.

They do it with ON DEMAND 135 operators & the airlines. Just to check your procedures without you knowing.

But I do not agree with "Zing's" assesment of "we're fucked". I think operators who understand what it really takes will have no problem adapting to what's coming. Had we paid attention to this problem years ago and addressed it properly we would not have arrived at an NTSB special report and presentation. I spoke at the USPA BOD meetings at SDC years ago saying if they wanted to promote skydiving more broadly to the public they had better clean up the jump plane accidents. I was received by the sound of crickets. Well, there you go. Chris, It is not a matter of what is coming, It's already here. In the last 4 months the FAA has issued 2 Airworthiness Directives for the Twin Otter directed right at skydiving operators. The first one dealt with Life Limited Parts. On the Twin Otter the Life Limited parts are found in their own manual, PSM1-6-11. Some one could argue that being that that manual is not part of the Limitations Section for the aircraft, then those limits are just recommended. I am sure that there were some operators that were not even aware of this manual because it is seperate from the Maintenance Manuals. Now they are MANDATORY. The second AD deals with the inspection program. deHavilland, now Viking, came out with an inspection program that is basically an inch thick. In it is included a Corrosion Inspection checklist. I, frankly, never knew an operator that complied with this program. The tried to get the operator that I used to work for to due it, but as always it involves time and money. Now this is MANDATORY. The increased oversight has started. There are some operators that better brace themselves. I would expect to see an increase in ramp inspections and maybe even "Ghost Riders". These are FAA Inspectors that pose as paying customers just so they can check things out incogneto

Basically a turbine engine, if it is maintained properly and overhauled at some given interval, will run forever. I know of PT6s that have over 100,000 total hours on them. Rebuilding an engine by repair does not constitute an overhaul. There are different specifications for each that are way to numerous to mention here. Let me be specific on this MANDATORY 12,000 hour TBO. This is, if the engine is new once it reaches 12,000 hours it must be overhauled, or once it accumilates 12,000 hours after its last overhaul. The PT6 class of engines are very reliable and if they are taken care of they will last forever.

Hey Chris; A -21 is basically a -27 derated to 550 hp fo use on early King Airs. I'am not quite sure how it was derated, but its not like a -34 install on a Twin where the derating factor is the red line on the torque gage. Not to many left in service.

There seems to be a huge misconseption about the term ON CONDITION. Whether you're Part 91, 135 or 121 you may operated ON CONDITION if specific criteria is met. Under 135 & 121 this criteria includes being on an Approved Program, regular Hot Section Inspections or Borescopes, Trend Monitoring, Overhauling components (i.e. Fuel Controls, etc) at their TBOs and your engines have to meet specific performance criteria as found in the AFM's Performance Section and Maintenance Manuals. Under Part 91 the only thing that is the same as 135 or 121 is that the engine(s) need to meet the Performance criteria. This applies to Piston aircraft also. Most operators are under the impression that if the engine(s) start, the aircraft can take-off and climb to altitude, then you're good to go. Not so. For example using a Twin Otter: Your operating on a hot, humid day. The pilot looks in the AFM to find the engine performance expected for that day on take-off. The pilot finds that he can expect a take-off torque of 46 psi instead of the 50 from the -27s. He taxis down for take-off, pulls on to the runway, advances the power levers, starts his roll and takes off. He only got 42 pounds of torque on one engine because it was temperature limted, the other was 47. This means that the one engine did not meet the performance standards to be ON CONDITION. Now this could have been a one time thing. It may be corrected by doing a simple Compressor Wash or may be the engine is out of rig. If it happens on a reoccuring basis then that definitly means that the engine does not meet the criteria for ON CONDITION and it is not airworthy. Also, if you look at Pratt & Whitney's PT6A Service Bulletin concerning TBOs and extensions, Pratt will not approve an ON CONDITION program for engines used on skydiving aircraft do to the way they are operated. It does state, though, that for ALL operators an engine MUST BE overhauled after accumilating 12,000 hours. The loop hole for skydiving operators is the way Part 91 is worded. It is my belief that the FAA may not hold operators to TBOs, but if the want to operate ON CONDITION they are going to have to do so under an Approved Program.