By Risk Management Magazine, U.S. Army Combat Readiness CenterMay 22, 2019
FORT RUCKER, Ala. (May 22, 2019) - When I arrived in Iraq, I was a new pilot out of flight school, chomping at the bit to contribute to the mission. After a week or so of right-seat rides, our unit was in full swing, supporting troop transport missions with our UH-60As. My second mission in country was to execute a six-hour flight in and around Baghdad. The temperature was typical for August, about 110-115 F.
My pilot in command and I ground taxied on alpha taxiway and prepared our aircraft for the health indicator test. After the HIT, we lifted to a 10-foot hover and noted our hover power. Everything was normal, and we set up to the northwest with clearance for a direct right turn out to cross the runway.
As we started our right-hand turn, I noted we were immediately in the midrange of our 30-minute turbine gas temperature (TGT) limit. I thought it was unusual since we weren't heavy but attributed it to the hot climate and lack of experience flying in country. The TGT eventually fell to a more acceptable range, dropping in and out of the 30-minute limit as we climbed to our cruise altitude even though we were 10 knots slower than originally planned.
When we arrived in Baghdad, we were calculating our TGT issue. As we transitioned across Baghdad International Airport, we were required to hold short of the runway. We noticed we were now hovering in the middle of our 30-minute TGT range, even though our torque was exactly what our performance planning card had predicted.
Our trail aircraft had a maintenance test pilot, so we explained our issue as we cross-checked the central display unit and pilot's display unit. He left the decision up to us as to whether we could continue to fly, so we chose to go on with the mission. We arrived at the forward arming and refueling point and took on a full load of gas.
The FARP was adjacent to the runway with two fuel trucks directly in front of it. As we climbed cautiously out of the FARP, we immediately started to lose rotor RPM. We were committed since we were directly over the fuel trucks, but it was at this point we received a low rotor RPM audio. The PC nosed the aircraft over to try to get some airspeed and quickly we got our RPM back to 100 percent, but we were barely complying with our hold-short-of-the-runway instructions. We ground taxied into the parking area, shut down and opened the engine cowlings to see if anything unusual was contributing to our TGT issue. We didn't see anything obvious, so we decided to continue with our mission, even though we now knew we had an issue with our TGT being high enough that we were getting into TGT limiting, thereby reducing our power margin.
For the rest of the day, we continued gingerly managing our TGT, taking very low takeoff angles to keep up our rotor RPM. As we would get to straight-and-level flight, the TGT would fall back into the lower end of the 30-minute limit. In one landing zone, we even made a modified roll-on landing and then repositioned to the pad that would give us the best chance for a rolling takeoff, all the while carefully bringing in power to clear obstacles. Upon returning to home station, we found something on the postflight that was the contributor to our TGT issues. The bleed air hose that fed the No. 1 engine had managed to separate from the engine.
I learned a number of things that day. First, trust your systems knowledge. We knew the whole day that our indications were not normal, yet we decided to continue. We didn't want to be the guys to impede a mission because we couldn't handle an "irregularity." Second, even though we were new to country, we learned that a power margin that small was not normal given the weights all day. Third, and most importantly, we were lucky not to get into a serious situation based on our aircraft performance. It could have been catastrophic if we had to use an evasive maneuver or more power than we needed for basic approaches and takeoffs. That day taught me that your system knowledge, along with applying good decision-making, will help you and your crew arrive safely.
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