KC-135

Flying Safety, Jan-Feb, 2006 by Bob Roukema

The KC-135 five- and 10-year mishap rates have never been lower. And, knock on wood, that trend will continue for a long time to come. However, we still continue to see events that indicate a lot of potential for more serious mishaps. Clear air turbulence was involved in the mishap sequence of events for the only Class A this past year. There was an air refueling-related Class B that sounds like it could have been much worse. We also continue to have a high number of near-midair collision reports and runway incursions that should make you wonder if we're being as safe as we can be.

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Some Comments About The Numbers

We've had a lot of discussion about various categories of mishaps. Sometimes that impacts the yearend statistics we have to discuss for the different aircraft. The most recent example of these evolving reporting requirements is the AFI 91-204, Aircraft Ground Operations (AGO), category. In FY05 we've had 21 Class C events where a maintainer was injured while working on the aircraft; the year before we had one Class C report filed in the same way. While this seems like a significant increase in the reported incidents, it is not. This past year, many incidents that would have been reported as ground or industrial events were reported as flight-related. To verify that, I checked with the Ground Safety guys. In FY04 we had 13 ground reports of the maintainers sustaining injuries while working on the aircraft and only one reported as flight-related. In FY05, we had 21 occurrences of a flight-related injury, all of which would have been reported differently in previous years. That's going to get fixed.

An interim change (IMC) to AFI 91-204, Safety Investigations and Reports, has been released. It redefines AGO as: "A mishap involving DoD aircraft, with an aircrew member on board, that occurs between engine start/shutdown and prior to/following intent for flight that results in reportable property damage or any injury or fatality. Damage to a missile prior to the completion of weapons upload procedures, or after initiation of weapons download procedures is a Missile mishap." This should reestablish some consistency in reporting.

Last year Major Harveaux wrote about an increase in lightning strikes. This year, the number of events is back down to FY03 rates. We also had a good drop in the number of air refueling-related Class C events, particularly Multi-Point Refueling System (MPRS)-related events; down to 12 overall Class C events from last year's 24. MPRS Class C events were down to four from a high of nine.

As far as the HAPs and HATRs, the overall numbers appear to be about the same from last year, with only minor differences in the reporting categories. For example, an FY04 report filed in the Air Traffic Control category may have been filed as a Near-Midair collision in FY05.

With all that in mind, I pulled out a few summaries from the categories we seem to see the most of.

Weather-Related

Since clear air turbulence was involved in our only Class A mishap, I'll cover it first.

The KC-135R was cruising at FL370 east of the southern Bahamas with 41 passengers. Factors considered necessary for clear-air turbulence were not forecasted and not expected. When the aircraft encountered the turbulence, it abruptly dropped 380 feet in six seconds, resulting in a -1.24G environment. The aircraft then quickly entered a -1.5G recovery. Several passenger injuries were incurred during the incident, and this mishap is categorized as a Class A mishap due to the nature of these injuries.

One other turbulence incident resulted in the minor injury of a passemger. In this Class C event, the aircraft was in IMC conditions at FL350, but no thunderstorms had been detected on the radar.

Four lightning strikes also occurred in FY05. This is down from a high of eight last year. Does everyone remember the five favorable conditions for a lightning strike from last year's KC-135 article?

Air Refueling-Related

The most severe refueling-related incident was a Class B, but could have been much worse.

Excessive closure was nearly catastrophic in a Class B refueling incident. The incident began with an unstable approach by the receiver in hazy conditions. It ended with the tanker missing the Boom Assembly and right hydraulics. The board identified several factors your safety office can brief you on, but both crews used up a lot of their luck that day.

There were nine reported incidents of ice shield damage. Two of these were attributed to landing with the boom in trail. Seven were from contacting the receiver aircraft. There were also two Class C events resulting from brute force disconnects. Many of these events sound remarkably similar and preventable. Here are a few:

* The boom ice shield was damaged during a night air refueling at 11,000 MSL, in visual meteorological conditions with light turbulence and haze. The receiver's first attempt at contact was unsuccessful after he did not stabilize in the contact position. In his second attempt, he was too high in elevation and did not arrest his forward movement.