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impact12

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Everything posted by impact12

  1. There is a Battle Damage Repair manual that has specific repairs in it for the C-130 -- been a little while since I worked out of it but I believe it is a TO 1C-130A-39. Is that what you are looking for?
  2. The P-3 props are manufactured from the same aluminum billet, have the same shaft diameter, same fairings, etc, but the ends are rounded off making them a little shrtoer the the C-130 54H60-91/117 blades. I have been working the flight test of the electronic propeller control system (EPCS) and NP2000 propellers for several years. The test results from the EPCS has been very favorable -- much better rpm control, better synch control, much more reliable and maintainable, much quieter inside the cargo area. We have a requirement and money to put EPCS on the LC-130H fleet. We have a requirement but no money for anything else. NP2000 uses the EPCS so you get all of the EPCS improvements on the NP2000 with additional thrust at lower airspeeds -- kind of an optimization between the performance of the old 3 bladed props and the 54H60 props. We will be heading to Edwards next month to complete the DT&E so that we have the data for a performance manual but as of yet, none of the MAJCOMs have stood up to a requirement for NP2000 propellers.
  3. My guess would be that you have a torn lip seal which means your fix includes removing the prop. Legally, you're okay to keep the engine running if you get a low oil light IF its not accompanied by RPM flux. If you are in a pinch, you could overservice slightly and fly the aircraft with the knowledge that you do have 3 more engines. If you sent me a TAR I'd tell you no unless bad guys are coming over the hill. I have told at least one crew to take off without a spinner (they were in a place where they were not wanted) but there is specific tech data that cautions against operating the aircraft with a known propeller discrepancy.
  4. I know of two possibilities. One is damaged (broken or missing) springs that are used to balance the forces on the levers. This is fairly easy to spot if you take the cover off. Second would be that the quadrant may be due an overhaul. I have tried for years to add quadrant overhauls to the PDM w/ no luck -- instead we do them "on-condition." Unfortunately, this often means you guys end up nursing loose or bound quadrants until we can get a UDLM team in place or limp into PDM. There are several drivers but the two most common problems in the quadrant that allows the levers to creep is either worn shims (pealable shims are used to set the gaps between each lever and these can become worn) or a worn shaft (that the levers ride on). Both conditions necessitate an overhaul. A solution that some play with is snugging up on the friction knob -- got to be careful here because the intention of the friction knob is to increase the friction axially -- if the shaft is worn and you try to overcome this looseness by tightening the friction knob, you can accelerate the damage to the pealable shims and cause the levers to bind.
  5. Need to be careful about reapplying insulation, especially if this is really a bleed air duct (as opposed to say an APU exhaust). Back in the bad old days before we had inconel ducts we used to find a lot of handprints between the insulation and the duct OD -- the oil from the hands of the technicians that were handling the ducts caused hot spots, deteriorated the duct material, which led to corrosion and catastrophic failure of the ducts. Considering the temps and pressures associated with the bleed air, you can do a huge amount of damage quickly!! This is why we in the SPO opted out of repairing bleed air ducts long ago.
  6. Prop brakes have been a perpetual problem since we had to change brake shoes during the mid 1980's and I do not see the situation changing in the near future. We have had RR investigate the problem to see if there was anything we could do differently in overhaul to make the current brakes last longer. Although there were a couple minor improvements made, the core issue was the shoes (duh). One thing that we did discover in the process is that the flushing procedure is questionable at best. When we looked at what actually happens when a prop brake is flushed, the most likely reason why the brake works during the subsequent FCF is because the solvent has dried out the surface of the pads, resulting in a (temporary) increase in the coefficient of friction. Although I have long suspected that the prop brake would not work again after it is fully oil soaked again, I have never been able to talk a unit into rechecking a prop brake after some time has passed. If I were at a unit I wouldn't be keen on rechecking the prop brake either because I'd be setting myself up for a RGB change. The reason I say that the situation will not change soon is that the engineering task to redesign the brake shoes is not being funded. Problem is that the way that the engine CIP community looks at safety necessitates that the safety issue get assessed wrt non recoverable in-flight shut downs (NRIFSD) and catastrophic mishaps. As a prop brake cannot cause a NRIFSD and is highly unlikely to cause a mishap (in isolation), the prop brake does not rate very high from a safety perspective in the CIP community. The other problem is that the overwhelming majority of discrepant prop brakes are identified during FCF which, in the USAF at least, are mostly accomplished in conjunction with PDM so the problem is somewhat hidden from the field. In summary, there really is no remedy for the current situation. Several years ago we elevated the problem thru HQ AFMC to HQ AMC and had the 4 buttons sign off on current guidance. Since then I did change the FCF guidance so that we are doing a few more FCFs in the field but O/W our hands appear to be tied.
  7. I recall seeing some pics of a tear down of the VH -- I believe FOD from a very old style potentiometer was determined to be causal in this incident.
  8. NULL is really the second best option. The advantage of NULL is that you eliminate the susceptibility of the fuel control system to input voltage anomalies but you always have the potential of overtemps and having to manage the TIT more closely. The reason(s) we chose the use of the inverter with the system in AUTO is as follows: 1. You get the benefits associated with the TD system. 2. You cut the deenergized side of the K44 relay out (except as a back up). 3. The DC side of the relay provide an additional backup through the reverse current relays so that if there is a problem on the ESS AC bus, the TD Amp doesn't respond. There is an effort to modify the TD Amps with solid state pots that will likely include a modification to the reference voltage circuit. We ran prototypes of the mod across both test benches and a test cell and the change precludes the TD Amp from responding to low voltage conditions down to about 30 volts where it cannot direct any changes to the TD valve.
  9. The reason we went to having the inverter in the DC position was because of the instability of the K44 relay which is one of the things we discovered from the Baghdad incident. The big problem, however, is the susceptibility of the TD Amp to input voltage anomalies. We have accomplished some testing recently that served to nail down the susceptibility (the reference circuit w/i the amp) and to correct the problem. Now that we know what the problem is, we should be able to correct the discrepancy by either fixing the amps or providing some undervoltage protection for the amps. Mike Fisher
  10. impact12

    8 bladed Prop

    Interesting thread - I’ve been involved with the testing of both the electronic propeller control system (EPCS) and the 8 bladed propeller (NP2000) for the last 6 years so maybe I can clear up some of the misconceptions and misinformation. If I miss something let me know. The reason the USAF is testing these is to determine suitability for the various missions supported by the C-130. EPCS offers a lot of potential R&M benefits as well as superior RPM control, synchrophasing, and unlimited transient response to throttle inputs. The design of the NP2000 blades offers additional thrust at take off and climb out speeds as well extremely low noise. The reason we opted to use USAF aircraft for this test is that we really needed a complete assessment of the systems (to include all of the sustainability/logistic issues) without any of the aerodynamic modifications added by Snow. The data developed by Snow was primarily to support a demo and so was not under anywhere near the rigor required to produce a performance manual -- we actually did use the data but primarily as a risk reduction tool. We have been using the aircraft at Schenectady and at Cheyenne for various reasons. We purposely structured the flight testing so that we could enter into operational flight testing in Antarctica ASAP while generating data that could be used to develop a performance manual. Additionally, having two aircraft is test allows us the flexibility to assess these systems while performing various missions. The results have been promising but not without any hitches. As much of the testing is in work or being reported on, it would be inappropriate to provide any details. Keeping in mind I am an engineer (not an FE) and not an operator, I can provide some general comments about the handling qualities. Many of the problems (high Vmca, high Vmcg, unacceptable stall characteristics) encountered by the C-130J were primarily because of constraints imposed by the FAA. Yes, Vmca and Vmcg will be a little higher but not excessively so. The power off stall characteristics of the NP2000 suffer a little in comparison to the 54H60 but the power on stall characteristics are almost identical to 54H60 configured aircraft -- I think this was a surprise to everyone involved. The stall characteristics we saw with the 54H60 propellers would preclude the legacy C-130E/H fleet from complying with FAA guidance without a stick pusher like the C-130J. Another comment I would add is the noise -- MUCH quieter both outside the aircraft and inside -- we are planning on characterizing this at WSMR later this year. In summary, the testing EPCS and NP2000 has been promising but the MAJCOMs are under a lot of pressure to stretch dollars so it is TBD whether these mods will transition to permanent configurations. I’ve attached some photo’s of the flight testing at Edwards, Schenectady, and Antarctica.
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