Ice is not Your Friend
COMPILED BY RISK MANAGEMENT STAFF
About a year after graduating flight school, I was conducting instrument meteorological conditions (IMC) training at a local airport with an instructor pilot. It was early spring and weather conditions were cloudy, with temperatures hovering at the freezing point. While planning for the mission, we received a valid weather brief stating there were no icing conditions forecasted or reported in our area. Since icing conditions were not uncommon that time of year, we were happy to have a brief that allowed us to fly and receive real-world training.
While going through the checklist during the run-up, we completed the blade deice check even though we were not anticipating icing conditions. The check verified everything worked properly and, as a precaution, we did use all of our anti-ice/deice equipment for the duration of the flight. We flew about two hours on a local instrument flight rules (IFR) flight plan and executed multiple instrument approaches while in the clouds.
At the beginning of the flight, as part of the normal instrument crosscheck, and since I was sitting in the right seat, I would check the ice rate meter. Being an inexperienced pilot, in both total time and weather conditions, I started missing the ice rate meter in my crosscheck. While on vectors for our final approach for the morning, I noticed the ice rate meter was indicating the presence of heavy icing conditions. We were flying at 4,000 feet mean sea level (2,000 feet above ground level) and 120 knots indicated airspeed (KIAS). Being that the ice rate meter was calibrated for 100 KIAS, it was reading slightly heavier icing conditions than we actually faced. However, we still wanted to exit the conditions as quickly as possible.
Since we were still in the clouds and the airport was IFR conditions at the time, we continued on our final vector and intercepted our final approach course. During the execution of the ILS and while descending on the glide slope, we heard a bang followed by a high-pitched whine. We checked the cockpit instruments and nothing was out of the ordinary. We continued on the glide slope and exited the clouds with an immediate turnout to the military ramp.
The post-flight inspection revealed the inlet for the No. 2 engine was damaged. Maintenance personnel did a more thorough inspection and could not see any foreign object damage in the engine. So what caused the bang we heard? It was determined that during the course of the flight, there was a moderate buildup of ice on parts of the helicopter. During the descent, while on glide slope, a piece of that ice shed into the No. 2 engine inlet. The result was a Class C mishap.
Valuable lessons were learned from this flight. It is important to receive a full and accurate weather brief. If you feel you did not get the information you were looking for, ask specific questions of that briefer. One piece of information I look for in a weather brief is the height of the cloud tops. It’s important during IFR flights if you encounter icing conditions.
Another lesson learned was that we could have reduced our airspeed during the approach. This slower airspeed would have slowed the melting process of the ice buildup on the helicopter and could have resulted in the safe execution of the approach and landing. Ice isn’t your friend, and Army aviators should always plan for dealing with it.