17 October 2006

TINS* Tuesday

(comes the time in most every Hawkeye flier's experience when they have to deal face-to-face with the hydraulic failure demon. The Hawkeye has two hydraulic systems -- one to drive the flight controls and another to drive the "auxiliary gear" which includes such minor items as landing gear, brakes, etc. In the event of a failure of the flight hydraulic system, the combined system can be used to drive the flight controls and alternate means, like blowing down the landing gear via compressed air bottle, comes into play. Lose both -- and you're exercising the silk veto ballot. Your humble scribe has probably seen more than his fair share owing to numerous post-maintenance check flights as a PMCF NFO, which has led to some personally memorable encounters with the mysteries of the Hawkeye hyraulic system. Today's recounting, in the true spirit of This is No S*** Tuesday, comes from the pages of Approach magazine, a publication of the Navy Safety Center for the recounting of "There I was..." stories for the education of the rest of the fleet. -- SJS)
Inadvertent Cross-Country
by LT Jerry Meyer/E-2C

"CICO, Flight! Confirm that's 'simulated' smoke in the FEC?" "Negative, actual, RO's going forward," replied the mission commander. And with that, my upcoming weekend went to "hell in a hand basket."

It started out as a good deal late morning hop. We would do a round robin to West Virginia and then down through South Carolina as a part of an NFO Stan check. We would be on deck with plenty of time to beat rush-hour traffic and start the weekend off right. Our squadron recently transitioned to the newest E-2C Hawkeye variant - the Hawkeye 2000. My cruise-experienced copilot signed for the plane, but I was the pilot at the controls (PAC). As a cruise experienced Plane Commander and Pilot NATOPS officer, I was comfortable with my knowledge and experience in the aircraft. The CIC crew consisted of two Super Stan checked CICO's and a very junior ACO. Crew composition was a big reason why this is an Approach article and not a mishap report.

About 1.5 hrs into the flight, we noticed a COMBINED HYD LOW LEVEL light on the caution panel with the associated Master Caution light. We immediately asked the CICO to send the RO into the forward equipment compartment to check the slug position in the combined hydraulic reservoir. We did not really think much of it because this light is not uncommon for an E-2 at altitude; usually increased air pressure brings it back into limits during descent. My copilot and I were surprised when the next thing we heard was, "We've got some smoke back here in the FEC, can't really tell where it's coming from." I was sure that we had our signals crossed with the CIC compartment and that they were initiating a typical Stan check FIRE, SMOKE, FUMES OF UNKNOWN ORIGIN drill.

After confirming that it indeed was not simulated, we immediately began stepping through the boldface procedures. As my copilot was donning his O2 mask, I turned the aircraft south toward the closest available divert field (Raleigh-Durham International). With the whole crew on O2, the next step called for attempting to isolate the source of the smoke/fire/fumes. The RO was unable to see from where the smoke was coming and it was getting worse. Accordingly, we immediately secured the vapor cycle and then generators in quick succession, causing the hydraulically powered E-GEN to kick on and power the electrical systems essential for flight.

At this point we had already declared an emergency and were given a clear descent into Raleigh. Unfortunately, we were still 40 miles away and at 19,000 feet. The next words we heard from the CICO made the hair on the back of my neck stand up although at the time I did not know why. "It's coming from the E-GEN," he shouted over ICS. Immediately my copilot and I looked at each other and simultaneously reached for the GEN switches to try and get a generator back online and remove power from the E-GEN. We wanted a generator back on line because without the E-GEN, we would be midnight in the cockpit (admittedly not a huge deal since it was day VMC). At this time, however, my copilot and I did not realize what was coming from the E-GEN. Well, we soon learned that hydraulic fluid was dumping out in "cups" from the front of the E-GEN. Our day was getting more complex by the minute.

I notified the crew of a possible complete loss of hydraulics and prepared them for the possibility of bailout as I leveled the aircraft and shallowed my rate of descent. Now I had to decide between trying to get on deck as soon as possible and trying to put the aircraft in a stable attitude in case the second hydraulic system also failed us and we were forced to bail out.
The good news, though only a small comfort to us at the time, was that the smoke appeared to be dissipating in the FEC, though we now had gallons of hydraulic fluid sprayed around the E-GEN shelf. In the NORMAL position with both generators online, the E-GEN still receives a small volume of hydraulic fluid to turn the generator at low RPM. This reduced flow prevents hydraulic shock when the E-GEN is activated. We came to the conclusion that what we previously thought was smoke was actually atomized hydraulic fluid seeping out of the E-GEN. By turning both generators off, we exacerbated this leak by directing the full 3000-psi hydraulic system pressure to the E-GEN. The already deteriorating flow valve failed under this increased strain.

Now 20 miles from the field, we at least had the problem pinpointed. We had a complete combined hydraulic failure. Luckily the E-2 has two separate hydraulic systems and both of them provide power to the flight controls. However, we would have to rely on the emergency mode of operation for the landing gear, flaps, and brakes and would not have the use of nose wheel steering. Oh, by the way, Raleigh does not have arresting gear. Grrreat!!
The flight hydraulic system seemed to be holding fine, though the flight controls were significantly more difficult to manipulate, almost like the BOOST OFF condition regularly practiced in T-2s in flight school.

After electrically lowering the flaps and blowing down the gear with a nitrogen charge, we were set for landing with "three down and locked" by 4 miles. In order to ensure we had brakes upon landing, I set the brakes into the aux position. With the brakes in aux, we have 15 applications available: 12 for the toe brakes and the remaining 3 reserved just for the PARKING/EMERGENCY brake. Upon landing, I initiated full reverse and all was normal until I realized that I had no aux brake applications and was still going 40 knots passing the three board. Sure, you are thinking, "He's still got plenty of time to stop," but a 48,000-lb E-2 is not going to stop in that distance using only reverse thrust. My copilot had already tried his brakes and backed me up on my procedures so our only recourse was to use the PARKING/EMERGENCY brake and hope we had the three remaining auxiliary applications as advertised. He smoothly pulled the emergency brake, and we skidded from 25 kts to full stop midway between the one and two boards. Safe on deck.

Not wanting to waste any time getting out of a plane with residual smoke and/or atomized hydraulic fluid, we turned the generators off and pulled condition levers to ground stop. Imagine my surprise when nothing happened! The ground stop position of the condition lever sends an electrical signal to shut down the engines, but because we turned off our generators and had no emergency generator, we were midnight in the cockpit. No electrical signal from the condition levers to the engines, no fuel chop. I quickly reached for the L GEN switch and flipped it on as my copilot went to feather on the right engine. The engines immediately began to spool down, whew!!

What did I get out of this experience besides an unplanned cross-country without a duffel bag? A bounty of valuable lessons:

Always confirm whether a procedure is "simulated" or "actual" before you go to GQ (or not).
Positively determine to the best of your ability which emergency you have and make sure the whole crew is on the same page. In this case, we were initially unsure whether we had a combined hydraulic problem (due to the light in the cockpit) or smoke/fire/fumes. In the case of a compound emergency, always go with the one that poses the more imminent threat. Smoke or fire in the E-2 is a very insidious problem, the lessons learned from past mishaps are written in blood.

Good CRM and a thorough preflight NATOPS brief enabled our crew to execute multiple procedures during the emergency. As briefed, the pilot turned towards the nearest suitable field, the copilot declared an emergency and backed the pilot up, and the CIC crew insured we were stepping through the checklist and continually updated us with the status of the situation in the FEC.

Emergency modes of operation for hydraulic subsystems are just that. They take longer, and may not work as advertised. Emergency brakes are supposed to allow for 12 toe brake and 3 emergency brake applications in the AUX mode. In this case I had about one and a half toe brake applications before they were useless. Since reverse thrust becomes ineffective as the aircraft decelerates, we were forced to use the parking/emergency brake as a last resort. This could have resulted in blown tires, fused brakes, or even a brake fire. Luckily, all we had to show for it were flat spots on the main mounts and rubber skid marks on the runway.

Just because you are stopped on the runway does not mean you can turn off your brain. Obviously, we were going to be midnight in the cockpit with the generators off, but we were eager to get out of the plane and forgot that the engines would not shut down via our selected method. We should have either used another method to mechanically secure the engines or left one of the generators on.

Just because a field is suitable for landing does not mean that it is going to be smooth sailing once your get there. We wanted to get the plane safe on deck as soon as possible. In this case that meant taking it to a field without arresting gear, support equipment (i.e. a huffer and a tow bar), proper security, or even appropriate load bearing strength for our single-wheeled main mount aircraft. Fortunately, we were able to rustle up the resources and the airport was very understanding of our predicament.

Finally, always bring a bingo bag with a change of clothes and some toiletries; you never know where you will end up on a round robin.

LT Meyer flies with VAW-125.