FY01 Engine-Related Mishap Summary

Flying Safety, Jan-Feb, 2002 by Bill Bradford, Capt Tom Fehringer, Rich Greenwood, John Maynard

(Information in this article came from Accident Investigation Board Reports and/or Part 1 of Safety Investigation Board Reports. None of this material was derived from privileged communications. Ed.)

Overview

Let's take a look at FY01 engine-related mishaps by beginning with a review of Figure 1, our standard leadoff chart. This figure illustrates the percentage of engine-related destroyed aircraft mishaps to all destroyed aircraft mishaps. It shows that engine-related destroyed aircraft mishaps are more than double the percentage for FY00. A look at the actual numbers of engine-related destroyed vs. total destroyed shows the split is 3/17 for FY00 but 8/21 for FY01. Before you jump to a conclusion that the sky is falling, however, take note that the numbers we're using are, relatively speaking, very small. A difference of one or two mishaps can result in significant changes in the percentages over the years and is responsible for the "Grandpa's Teeth" shape of the chart. For the past eight years this percentage has averaged about 30 percent. It is also worthy to note that over the last five years, 29 of the 34 engine-related destroyed aircraft have been in the single-engine F-16 aircraft.

Next, in Figure 2 (right), we show the drivers of the FY01 Destroyed Aircraft mishaps. (After all, what would a magazine article written by engineers be without pie charts?) As said before, although Figure 1 might lead you to believe the engine-related percentage is high, we see the 'Operations' portion of the pie is even higher. Details of the non-engine-related mishaps can be found in the aircraft-specific articles elsewhere in this issue. Conspicuous by their absence this year, are destroyed aircraft due to bird strikes--good news for aviators and the USAF BASH Team (the birds, too!).

Figure 4 (right) provides a snapshot of mishap factors. Of the eight engine-related mishaps that resulted in a destroyed aircraft for FY01, one of them was directly related to incorrect engine assembly procedures at depot ("Maintenance"). One was attributed solely to field maintenance procedures (another "Maintenance"), while another was a combination of field maintenance with an assist from the pilot (score one each for "Maintenance" and "Operations"). Two of the mishaps involved failure modes which have caused mishaps before and are currently being addressed through component upgrades ("Logistics"). And there were three in the "Other" category--one from a previously undetected FOD event and two that remain "unknown." Obviously, attention to detail in the assembly and maintenance of engines is of paramount importance in keeping a single-engine fleet safe, along with aggressive incorporation of design fixes for known problems.

Engine-Related Destroyed Aircraft By Engine Section

Examining particular engine areas that brought down airplanes in FY01, we present Figure 3 (left). Except for engine bearings, what we have here is pretty much "one-sies," with no "two-sies." In the case of the single "Unknown," the mishap aircraft impacted the water and wasn't recovered, so the engine couldn't be inspected to conclusively determine failure cause.

F-15 and F-16 Mishap Rates

Now let's look at the engine-related destroyed aircraft rates for two of the more "visible" aircraft, the F-15 and the F-16. The rates are in destroyed aircraft per 100,000 engine flight hours (EFH). Table 1 shows the rates for the last three years for the three different engines used in the F-15.

Pretty impressive, huh? It's obvious that a sound design, good maintenance practices, aggressive incorporation of fixes for known problems and detailed inspections all contributed to this impressive record. Having a second engine doesn't hurt either!

On the F-16 side of the house, the numbers are shown in Table 2.

FY01 looks better than FY99, but not nearly as good as FY00. As pointed out before, however, with the small numbers we're looking at, the statistical significance of these rates is debatable. We've already discussed the engine areas and factors that contributed to this year's rates. Now let's take a look at each of these eight mishaps in more detail, including the one engine-related mishap that resulted in a destroyed A-10.

F110 Engine-Related Mishaps

There were five engine-related destroyed aircraft mishaps in the USAF F110 engine family, all of them occurring in the F-16 aircraft. Four involved the F110-GE-100 and one involved the F110GE-129.

The first F110-GE--100 mishap occurred during a local training mission when the mishap pilot (MP) experienced an engine rumble. After frying to clear the rumble/noise using throttle movements, the MP turned the mishap aircraft (MA) back toward home station. The MA caught fire during the return leg and the MP shut down the engine, but the fire continued. The MP ejected safely and the aircraft impacted the water approximately 20 miles offshore. The search effort for the aircraft and engine proved futile and was called off after two weeks. To this date the mishap aircraft has not been recovered.