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slepowron
Dołączył: 15 Paź 2005
Posty: 1520
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Skąd: KOAK
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 Wysłany: Pon 20:00, 18 Gru 2006 Temat postu: wylaczanie silnikow w F-16 |
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Wiemy juz ze wbrew wielu plotkom nie trzeba czekac 10 minut z silnikiem na niskich obrotach przed wylaczniem. Silnik wylacza sie natychmiast po ustawieniu przepustnicy na "idle' i poczekaniu kilka sekund jak obroty sie ustabilizuja. Natomiast w starszych silnikach do F-16 (seria -220 i 220E) trzeba bylo tuz przed wylaczeniem znacznie ... zwiekszyc obroty silnika. Tutaj gosc tlumaczy o co to chodzilo, calosc jest bardzo techniczna wiec nie podejmuje sie tego tlumaczyc. W kazdym razie polskie silniki F-100 sa serii -229 i ich to niedotyczy.
| Cytat: | The "scavenge" or "rev up" at engine shut-down for the -200 and -220/-220E engines was to recover more oil from the engine's bearing cavities and pump it to the tank. At idle, oil would tend to gather in the bearing cavities. While not harmful to the engine, the oil would tend leak from the cavities after shut-down when the breather or "head-pressure" on the system was removed.
Many pilots would not scavenge properly (yes they do have faults) and engine troops were often called to leaking aircraft where the scavenge was re-accomplished to eliminate the possibility of a "real" oil leak. If the timing of the procedure wasn't followed CONSISTENTLY, it would not work as intended and leakage or bad oil level recording would result. This was key to not over-servicing the engine's oil tank and cause more leakage.
This became very evident in the late 90's as the engines aged and prior to the installation of an "anti-siphon" tube during a modification or TCTO to the engines. This would help break a suction that would form on the #5 bearing cavity and cause leakage from that area. (I think there were 3 variations of the mod before they got it right)
The "fuel-dump" at shut-down was the result of moving the throttle from idle to cut-off. The resulting motion of the throttle linkage, on the main fuel control, would cause a signal pressure line to cut fuel pressure to the open side, of the pressurizing and dump valve on the engine. This valve was responsible for dumping the fuel, when cut-off was selected, there-by diverting the fuel flow from the main fuel pump (which is still spinning with the engine) overboard so that the flame was exhausted inside the combustion chamber.
This dump can even be seen during old movies of early jet airliners when engines were shut down. J-57s, J-75, and most others all dumped fuel at shut-down. This was no longer acceptable with EPA (and other) regulations, and ground-crews had to catch this fuel in buckets or fabricated "catch-cans" pinned to the F-16's tail-hook area. These were later dumped in the proper recyclable or disposal areas near the flight line.
Newer -229 models of the F100 engine still "dump" fuel, but it is sent into a fuel manifold on the engine that is lower in pressure, so that the fuel is by-passed internally and recycled into the fuel system.
The "scavenge" of the oil system is no longer required on the -229 as the oil system has been redesigned and does not require the additional RPM to perform the job.
Moral: "The -229 isn't your Father's F100...." to coin a famous phrase. |
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