Page 20 - Volume 13 Number 2

A cut-away view of a PT6 engine with an arrow pointing to the containment ring – a heavy band of metal that surrounds the PT disk(s) and protects against PT disk blade fragments being released.
operating with the detector test points inside their cowlings and no chip annunciators.
The 200, receiving its Federal Aviation Administration (FAA) certification in late 1973, was the first King Air to have the left and right engine chip detectors wiring into the annunciator panel circuitry. The annunciators were in the warning panel – the one with all the red lights. Red implies “emergency,” so they are very important lights that almost always involve some checklist steps that should be memorized.
So, what did the Emergency Checklist tell the pilot to do? Absolutely nothing! Why? Because the first 200 checklists had no procedure whatsoever dealing with this newly-installed annunciator! It appears the design engineers snuck an annunciator in without bothering to notify the POH writers.
Dave Simon, one of Beech Aircraft’s marketing staff on the international sales team, was the first pilot to experience the illumination of a chip light while flying one of the early 200s. He dutifully searched the checklist and, as I’ve made obvious, found nothing! The engine was running just fine, so he chose to continue the flight. Yes, you guessed it: Within about 30 minutes the engine blew up! Dave made a successful single engine landing and the Beechcraft team quickly verified that indeed the RGB had uncoupled. Hmmm ... perhaps we’d better address that annunciator in the POH!
A POH and checklist revision was quickly forthcoming. In fact, all of the King Air models then being produced – C90, E90, A100 and 200 – started being equipped with the annunciators and their POHs/Checklists had the procedure added. And what was the procedure? “If conditions permit, shut down the engine.” In fact, some models merely added “Chip Detector Illumination” to the title of the already existing checklist “Engine Fire in Flight.” Pull the Condition Lever and shut that sucker down!
18 • KING AIR MAGAZINE
As Mr. Simon’s incident (and now some others) showed, there could be no abnormal engine indications whatsoever making themselves known before the engine turned into a bomb. “If conditions permit” has never been clearly defined. The consensus seems to be that shutting down an engine because of a chip light would not be wise if the other engine had already been shut down for some other reason! Likewise, perhaps waiting to either land or execute a successful two-engine missed approach might be the wise course of action if the light illuminated while inside the FAF while executing an ILS or LPV approach with the weather hovering right at minimums.
I have two personal experiences to tell you about. One of my clients with whom I conducted recurrent training had the light illuminate on a sunny day while departing Rock Springs, Wyoming, on a flight back to Portland, Oregon. The annunciator appeared just as they were leaving the Rock Springs’ airspace. The 200 they were flying was used as a corporate shuttle and most seats were filled. Being in such good conditions, the crew went ahead and secured the engine. As they returned to Rock Springs for an uneventful single- engine landing, they hoped that the light had been triggered by some metallic “lint” instead of a significant piece of metal. This mysterious lint has indeed been the cause of some chip lights. In these cases, usually the main oil filter is inspected and, if nothing significant is found, the aircraft is authorized to fly 10 hours more before another check. If things are still copacetic on the follow-up check, then no further action is required. (One theory is that this lint may be manufacturing residue that was not thoroughly flushed away after the engine was manufactured or overhauled.)
Well, the crew’s hopes of “nothing major” were dashed when, in their words, “We could do chin-ups on the prop blade!” The gearbox had frozen solid with contamination.
A year or two after this incident, I was conducting recurrent training for the pilots of an early C90 based at Gillespie Field (KSEE) near San Diego, California. We flew east to avoid the busy San Diego area, and while doing air work near Thermal, California, the chip detector on the left side came on. The weather was perfect, we were light with only about half fuel and three people (all pilots) on board, so we went ahead and shut the engine down. Being close to Gillespie, we decided to return to that airport where they had their own mechanic available. As we flew, having declared an emergency with ATC, I was pleased to see that occasionally the three- blade prop would turn slightly as we changed speed or configuration. “At least the gearbox isn’t frozen, unlike the Rock Springs case” I thought to myself. “Probably gonna be a little lint.”
FEBRUARY 2019