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Over Water, Out of Power

Over Water, Out of Power

CHIEF WARRANT OFFICER 3 MATTHEW HOPPER

Over the last 18 years, there have been many events I’ve written about. Most would probably be good reads, but one in particular sticks out — the infamous dual-engine rollback in a UH-60A over ALANA intersection just south of the Honolulu VOR.

The flight started routinely with an instrument flight rule departure from Bradshaw Army Airfield on the big island of Hawaii. We were en route to Wheeler AAF on Oahu. I was the pilot in command of the flight, and my pilot that day was another experienced PC in the company. I had about 2,000 hours of flight time, and the PI was somewhere close to 1,000 hours. Needless to say, it was a nice change from doing readiness level progressions or evaluations.

Shortly after takeoff we settled in for a nice, two-hour flight back to Oahu in mostly visual meteorological conditions. I would have preferred to be operating under visual flight rules at 500 feet back to Oahu to take in the sights, but it was against brigade policy to fly single-ship VFR inter-island. Prior to this incident, I really did not understand the point of that rule. It soon became very clear.

The first hour and a half of the flight was uneventful. We had been at 10,000 feet and kept getting altitude step-downs from approach control. We eventually ended up at 6,000 feet and two to three miles from ALANA intersection, which is about 13 miles south of the Honolulu VOR and 12 miles from the closest piece of land. As we approached ALANA, I started my right turn inbound to the VOR. That’s when we heard something every pilot hates to hear — a change in engine noise.

Everything seemed like it was in slow motion. I was the pilot on the controls and when I heard the engines spooling down, I looked at the pilot’s display unit and saw both engines and the rotor RPM dropping. At first I thought we had oscillations, which I’ve seen before; but when all three came down below 95 percent, I announced decreasing RPMs and lowered the collective slightly and slammed the increase/decrease switch full forward. I would later find out the entire crew thought I was messing around and introducing an emergency procedure.

As soon as the low rotor horn sounded, they quickly realized this was for real. I announced autorotation and lowered the collective completely. I then made a sharp right turn to avoid going in the next set of clouds at our 12 o’clock. At this point we were about five to 10 seconds into the emergency. As I entered the auto and started my right turn, I could see Jason, the PI, was looking at the central display unit and caution advisory, trying to figure out what had just happened. I asked him, “Jason, which is the low engine?” He responded with, “Matt, they are both low”.

I then thought to myself, “What would cause both engines to go low but not shut down? Jason must be looking at this wrong.” All the while, I was trying to establish a steady state for the autorotation. At this point I had slowed the aircraft from 110 knots to 85 knots or so and started to lower the nose and turn toward a large ship inbound to Oahu. I had no intentions of landing on the ship, and, yes, I’ve been asked why I turned toward it. I just wanted to be close to something if it turned out we had to swim that day.

In the meantime, while I was getting us established into an autorotation, Jason was still troubleshooting the EP. The only thing we knew for sure was that we were dealing with something neither of us had ever seen. I then asked Jason again, “Which is the low engine?” He responded with, “Matt, I told you, they are both low.” Of course, it was in a much more forceful and slightly annoyed voice the second time. I then took a look inside for a half second and, sure enough, both engines were low. My eyes were immediately drawn to the NG. They were both indicating about 65 percent, which, for a Black Hawk means the engines had rolled back to idle.

I can’t remember exactly where the ENG RPM ended up, but we maintained the rotor at approximately 102-103 percent. I then looked outside and said to Jason, “That makes no sense at all.” To which he said, “I agree,” with a few choice words in the middle.

He then announced he was taking No. 2 to lockout. I replied, “Roger, No. 2 to lockout.” But as soon as he put his hand on the engine power control lever, the engines started increasing RPM. Now, mind you, this had nothing to do with moving a control lever. Jason had merely placed his hand on it and not moved a thing.

As soon as the engines started their upward climb, I said, “Hold on. Leave it alone for a second.” At this point I know there will be plenty of you second guessing this decision, but put yourself in my shoes for a minute. I had never seen two engines decrease RPM before and now they were coming back to life. I did not want to do anything that may aggravate the situation. Plus, we still had 4,000 feet or so to figure this out before we were swimming.

Jason then stopped and held his hand on the PCL but did not take it to lockout. As soon as the engines got up around 95 percent, which felt like an hour, I started to slowly increase the collective. You could feel the rotor starting to take the load and we heard the whine of the engines as they started to couple with the rotor again.

The engines and rotor met up close to 98 percent before both engines started to head south again. This time, they only went down to 90 percent and immediately started their climb back up to 100 percent. To me this looked much more familiar. I told Jason, “Hey, it looks like they are oscillating. I’m going to start pulling collective and we’ll see what happens. If the engines go below 95 percent this time, get No. 2 to lockout.” He said OK. As the engines and rotor coupled again, all three started to oscillate from about 95 percent up to 102 percent. We then leveled out somewhere in between 2,000 and 3,000 feet.

During this process, HCF approach had been screaming on the radio. Previously, Jason made the mayday call after the entry into the autorotation, but we did not have time up until this point to give them any of the details they wanted so badly. Jason got on the radio and explained the situation and, after a lot of back and forth, finally told them we were landing on 4R at Honolulu. They were not happy about that at all. They wanted us to continue to Wheeler AAF, but given what we had and the lack of really knowing what we were dealing with, Jason and I thought it best to get this thing on the ground ASAP.

Jason’s hand never left the No. 2 engine power control lever during his conversation with approach and his eyes never left the pilot’s display unit. We talked about it the whole way in. We know the EP for oscillations, but because this EP did not come on as normal oscillations, we did not want to compound the situation unless we were no-kidding getting ready to go into the water.

The rest of the flight, which lasted less than 10 minutes, was, for the most part, uneventful, barring the pucker factor every time the oscillations went close to 95 percent. We landed at Honolulu and started making our calls. The first one was to the commander and then on down the list. After everyone was notified and the ball was rolling on aircraft and crew recovery, we had some time to take in what just happened.

We got the crew together and started talking. The biggest takeaway — or surprise, if you will — was there was never any overreaction. Our crew chief, Andrew, kind of chuckled because he said that it sounded like Jason and I were just having a conversation without much emotion involved. I then chuckled a little bit because I was really happy I still had clean pants. At that point, we felt we all performed as a crew in exactly the manner we were trained. Take your time to identify the emergency procedure and don’t compound an already bad situation. We had time; we started this EP at 6,000 feet and 110 knots. Our initial reaction was to take one engine to lockout, but, not knowing exactly what we were dealing with, who’s to say that would not have made the situation worse.

The next few weeks were excruciatingly painful with the troubleshooting that was going on from some of our peers and superiors. If I remember correctly, the battalion commander’s first question to the BAMO was, “What did they do wrong?” I found that comment humorous to say the least. How quickly we in aviation are to judge things we don’t understand. I was also asked numerous times why I did not jettison the doors, to which I replied, “Where do you think the doors are going to go in an autorotation?” Some of you may find that question crazy, but I can honestly say that’s the most common question I received after all of this went down.

Anyway, there were many, many people who said and still say a dual-engine rollback in a Black Hawk is impossible. To them I say read the Flightfax article from May 1999 and get back to me. To everyone else, I say this: Dual-engine rollback happens. Do a quick Google search and you can read all about it. I was told there was not one specific cause. However, they did find a leak in the anti-ice start bleed valve that caused heat damage to one of the ECUs.

They also found a broken or bad wire that came from or went to an engine speed potentiometer. Just to set the record straight here, I am not a maintenance test pilot, but it was explained to me like this: One engine went low because of an overheated ECU and, based on the faulty potentiometer, the other engine went with it. When the ECU cooled down, they came back. That was a good enough explanation for me.

I know all the representatives from the appropriate companies were involved and eventually figured it out, or at least got it back together to the point where they said it would not happen again. I have no idea if our dual-engine rollback was caused by the same malfunction that caused all of the rollbacks in 90s, but I can assure you, the engines rolled back. Had we been at 500 feet and not 6,000 feet, there is a pretty good chance we would have been swimming back to Oahu.

Of course, now that we know dual-engine rollback exists, I don’t think it would take me long to diagnose and take action. If engine power control levers are set to fly and both engine NGs are low, I’m taking one to lockout, no questions asked.

What I’m trying to share is the fact that nothing is set in stone. Just because it’s not in Chapter 9 of your operator’s manual does not mean it can’t happen or does not exist. Of course the -10 does address engine RPM being low and checking the increase/decrease switch, which we did, but it had zero effect. I had never heard of dual-engine rollback until the day I had to deal with it in a real-world incident. After I described what I had seen, I must have heard 10 stories about people familiar with it. That’s also when I was made aware of the Flightfax article from 1999.

After the smoke settled a bit, Jason posted the information on Hawkdriver.com, trying to get some information about rollback. A few folks chimed in with actual accounts. Still, to this day, I have yet to see anything or hear anything other than the following statement: “It can’t happen.” To that, I politely respond, “You’re wrong!”

  • 1 November 2015
  • Author: Army Safety
  • Number of views: 10308
  • Comments: 0
Categories: On-DutyAviation
Tags: rollback
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