Autorotation is Not a Low Rotor RPM Emergency Procedure

Especially when you’re two miles out at sea.

Picture this: An R22 helicopter without floats operating two miles off the coast of Miami, FL. On board is the CFI-rated pilot with 600 790 hours of total flight time and the private pilot rated “passenger” with 115 hours total flight time. They’re operating at about 40 knots 100 feet above the waves on an aerial photo mission, photographing boats. The wind in Miami, 13 miles away, is from 120 at 13 knots and it’s 26°C with a dew point of 21°C, resulting in a balmy 74% humidity.

The pilot had just completed a 180° turn to the south when the low rotor RPM horn sounds.

The pilot adjusts the throttle to compensate — in other words, we should assume that he adds throttle. The horn stops blaring, but 3 seconds later, it does it again.

So what does the pilot do? Despite the fact that the helicopter does not have floats, he enters an autorotation. The helicopter crash-lands in the ocean, the occupants escape, and the helicopter sinks. The pilots are rescued 10 minutes later by a privately owned boat. The helicopter is left unrecovered (so far) in 150-250 feet of seawater.

What We Don’t Know

There are a few things we don’t know that could explain the reason for the low rotor RPM horn:

  • How much did the pilots and their equipment weight? An R22 Beta (not Beta II) is a very small helicopter. Although they had burned off 45 minutes of fuel, there is a possibility that they were still heavy for the flight conditions.
  • Which direction did they turn? A turn that would have put them into a tailwind situation — especially at low speed — could rob them of airspeed. If airspeed dropped below ETL, the helicopter would have to work harder to stay in the air.
  • What speed were they operating at? Without the benefit of forward airspeed and effective translational lift, the helicopter would have to work harder to stay in the air. If the speed was close to zero, the aircraft might have gotten into a settling with power situation. The natural (but incorrect) reaction of increasing the collective to arrest the rate of descent could have triggered a low rotor RPM warning if available power was exceeded.
  • Were the engine and its components functioning properly? If the engine or magnetos were not performing to specifications, the resulting reduction of engine power could cause a low rotor RPM horn. We have to assume the engine was still running because the NTSB report didn’t mention an engine failure.

But regardless of the reason for the low rotor RPM horn, it’s the pilot’s decision to perform an autorotation to into the ocean that needs to be questioned.

The Robinson Low Rotor Horn

In a Robinson helicopter, the rotor RPM green arc is 101% to 104%. (Please don’t ask why; I don’t know. Yes, it is weird.) The low rotor RPM warning system is designed to alert the pilot at 97% RPM. (See it in action for yourself here.) This is a very early warning. The idea is that if rotor RPM is deteriorating, once it gets past a certain point, it could could become unrecoverable very quickly. The earlier the pilot is warned, the better off he is.

At the Robinson factory safety course — and, one might assume, at many flight schools that train in Robinsons — pilots are taught that a Robinson can generally fly at an RPM of 80% plus 1% per 1000 feet of density altitude. Given the temperature, dew point, altitude, and altimeter setting (30.01), the density altitude was 1,612 feet. That means that the helicopter should have been capable of flight when operating at only 82% RPM.

I need to stress here that this is a general rule of thumb. Do not attempt to fly around at low rotor RPM to test this. While it’s true that my flight instructor at the Robinson safety course had me fly for a few minutes in the Long Beach, CA area at 90% RPM with the horn blaring just to prove that flight was possible, RPM is not something we play with in non-training situations. The formula is simple: RPM = life.

Low Rotor RPM Emergency Procedures

The Robinson R22 Pilot’s Operating Handbook is quite specific on what to do in the event of a low rotor RPM warning. On page 3-10, in the red-tabbed “Emergency Procedures” section, it states:

A horn and an illuminated caution light indicates that rotor RPM may be below safe limits. To restore RPM, immediately roll throttle on, lower collective and, in forward flight, apply aft cyclic.

The NTSB report indicates that the pilot initially “adjusted the throttle to compensate for the [low rotor RPM warning] condition” and was immediately rewarded with recovery. But that was followed by the horn sounding again only 3 seconds later.

It had to be scary for the pilot. After all, he’s only 100 feet above the water and he’s supposed to react by lowering the collective. But the emergency procedure and repetitive training doesn’t tell us to enter an autorotation, which would be a full-down reduction of the collective. The reduction of the collective, coordinated with the rolling on of the throttle, should be slight — perhaps an inch or so. This reduces drag on the blades while the increased throttle provides power to increase their RPM.

What Was the RPM?

One of the things we don’t know is what the RPM was when the pilot decided to enter autorotation. If it had deteriorated to the point where autorotation and cyclic flare were the only tools to recover RPM, his decision was probably a good one. Better to hit the water relatively softly than from 100 feet up, falling like a brick.

If RPM had deteriorated to that point that quickly, however, it’s important to recover the aircraft to learn why. Other than a complete engine failure — which was not mentioned in the report — it’s hard to imagine what would cause RPM to drop enough to warrant such a drastic recovery action.

Who Was Flying?

There may be more to this than what meets the eye.

The helicopter was operated by Helicopter Academy, a flight school with locations across the U.S. The school’s Web site clearly advertises it as a low-cost training company:

$250 PER HOUR R22 HELICOPTER TRAINING TIME BARGAIN and we are the ONLY company in the world that can guarantee you a job.  We operate a fleet of helicopters and like other schools our insurance requires 300 hours helicopter time and an instructor’s rating to fly for us. We train you to work for us and offer a job to all graduates, including transfer student and instructors who can’t get jobs elsewhere.

Helicopter Academy’s other business is BoatPix, which uses helicopters to photograph boats and then sells the photos to the boat owners and others. It’s widely known that BoatPix pilots pay BoatPix (or Helicopter Academy) for the time they fly aerial photo missions. The company’s Web site alludes to this:

…you pay for the first 100 hours at $250/hr, the second 100 hours at $200/hr and the third 100 hours at $150/hr….It’s  $25,000 for the first 100 hours where you’ll do mostly training, $20,000 for hours 100  through 200 where we’ll introduce you to our photo contract which will subsidize your flying and $15,000 for hours 200 through 300 where you’ll do almost exclusively photo and will learn this skill that is valuable to our photo contract and making you a valuable pilot to us.

I added the emphasis in the above quote. It begs the question: who was actually flying this aircraft? The NTSB report suggests that it was the 600791-hour CFI. But was that really the case? Was the 115-hour private pilot paying $200/hour to be “introduced” to the photo contract — as a pilot — while the 600791-hour CFI took the photos?

High Risk Operations

In March 1999, Robinson Helicopter issued Safety Notice SN-34. The latest version of this Safety Notice is dated April 2009. Titled “Aerial Survey and Photo Flights – Very High Risk,” it starts out saying:

There is a misconception that aerial survey and photo flights can be flown safely by low time pilots. Not true. There have been numerous fatal accidents during aerial survey and photo flights, including several involving Robinson helicopters.

It goes on to list some of the possible dangers of low time pilots conducting aerial photo flights. It also makes some recommendations for minimum requirements for aerial photo/survey pilots, including a minimum of 500 hours pilot-in-command. BoatPix is one of the operations that has chosen to ignore this recommendation.

My question to helicopter pilot wannabes out there: Are you that desperate to become a pilot that you’re willing to trade your safety for flight time?

Pilot Experience and Decision-Making

What it all comes down to is whether the pilot made the correct decision for the situation he found himself in. I’m not convinced that entering autorotation over the ocean on hearing a low rotor RPM warning horn is the correct decision.

True, both pilots walked (or perhaps I should say, swam) away. But if the rotor RPM could have been brought back into the green while in flight — something a well-trained or experienced pilot could have accomplished if there wasn’t a mechanical problem — the watery autorotation and the resulting loss of the aircraft could have been avoided.

Hopefully, the Probable Cause report for this accident will shed some light on what really happened. Until then, it certainly gives pilots some food for thought.

November 1, 2011 Update: The Probable Cause report doesn’t add much to what’s reported here other than to clarify airspeed and PIC experience. The official Probable Cause is “A loss of main rotor rpm for undetermined reasons.”

Update, March 17, 2012: Just found another accident report with someone else using autorotation as a cure for low rotor RPM. He crashed, too.

5 thoughts on “Autorotation is Not a Low Rotor RPM Emergency Procedure

  1. I’ve looked into BoatPix and know several of their current and former pilots. One of my first questions for every one of them was about SN-34, and whether they felt they had received the training they needed to fly a mission that was specifically called out in the POH as hazardous. While I don’t know the 2 that were involved in this incident, I do know a little about their operation. They train to fly the photo contracts. Many of the pilots don’t get their instrument rating, and they start flying photo contracts with an experienced CFI after they have their PPL, so they have considerable experience flying the photo contracts. The pilots are taught to fly the photo portion of the flight in a specific way that accounts for both aeronautical and photographic conditions. They have a briefing document that lays out the pilot’s and photographer’s responsibilities. They fly the photo flights like any other commercial operation, where the pilots have to be cognizant of safe and efficient operating procedures. With 600 hrs, the CFI in this case also met the recommended experience of SN-34.

    I compare their training to the training my school gives their CFIs for flying the “flight instruction mission”. I spent a few hours learning to fly left seat. None of that time was spent flying with the cyclic at chest level instead of in my lap, where the T-bar puts it for the instructor. The balance of my CFI training was learning touchdown autorotations. Maybe I spent 15 hours on the whole affair, and I won’t even go into the ground portion of the CFI. Never once during my CFI training did I practice wrestling the controls from the instructor. Or salvaging an autorotation, quick stop, hover auto, or slope landing gone bad. Or, for that matter, even talking the instructor through fixing a bad approach. In most cases, I was given minimal verbal training on recovering a dangerous situation. When I was getting signed off for my check ride, all I could think was “Wow, that’s it? They’d really send me out to teach tomorrow?”

    Looking back, it explains my instructors’ behavior during my early lessons–when they were fresh out of their CFIs and I didn’t know better. I was the first student my instructor demonstrated an auto for, and it was probably the first one he’d done in over 100 hrs (and no telling how many months). It was awful, and it left an impression on me that I had to fight throughout my training. He was also heavy on the controls, to the point where I wasn’t flying a good bit of the time on many maneuvers (which I learned on a stage check, where the CP had his hands in his lap and my turning autos were all over the place). I later learned that the school I went to purposefully puts new students with new instructors. Since the students are doing low-risk maneuvers (mostly S&L, hovering, approaches), the instructor has some time to figure out how to teach. The students effectively subsidize the instructor’s CFI training while paying for sub-par training. How wrong is that? That school has also had 3 incidents that I know of that I think reflect the training their CFIs get. 2 were hover autos where the instructor wasn’t prepared for the possibility that a student might roll the throttle up instead of down. Both led to hard landings, after one of which the instructor flew the aircraft back to base with a dent in the tail cone (!!!). The other was a pinnacle approach where the instructor allowed the sink rate to get out of control, and ended up wrecking the helicopter.

    All that said, I know there are untold number of times where instructors at that school avoided an incident–by luck, training, good judgment, or experience. Considering that Helicopter Academy has 4 times the aircraft that this school has, and that they are doing a mission that is “Very High Risk”, their instructors get it right most of the time and should be given credit for that.

    Being a low time pilot sucks. We have to get experience somehow. It should be flying left seat with an experienced pilot for a long while, but those guys and their employers don’t want us. On top of that, any pilot with experience runs from flight training as fast as he can. So, flight training, photo flights, powerline/pipeline patrol–thems’ our options, not that they’re great options, but it’s what we have to live with.

    • Chris: It’s definitely wrong for a new CFI to teach a new student. That’s not fair to the student at all. In general, I don’t like the way helicopter (or airplane, for that matter) instruction works. How could they possibly let a 300-hour pilot TEACH a brand new student? But it’s true: an experienced pilot doesn’t want to teach.

      I’ve flown on three long cross country flights with three different 300-hour CFIs. I was pretty amazed by what I saw. Some of them lacked basic skills like cross-country planning, radio communication with a tower, and following instructions. Others had difficulty performing basic maneuvers — like landing! I know I flew like them once, but I also knew that I never had the responsibility to teach someone else. I don’t think a CFI should be allowed to teach until he has 500 hours or can demonstrate that he knows what he’s doing.

      But there’s no substitute for real-life experience.

      The point of this post is that the pilot in command — whoever that REALLY was — chose to perform an autorotation into the ocean without floats rather than attempt to control rotor RPM well enough to keep flying and bring it back to shore. We don’t have the details — perhaps a real mechanical problem made RPM recovery impossible. But as the report reads, it appears that he tried just once to recover RPM. An autorotation from 100 feet is always risky; was that the only answer? If there was no real mechanical problem and the RPM loss was due to flying technique, I think the pilot made an error of judgment. That error could be due to lack of experience. That’s my point here.

      As for getting experience flying left seat with an experienced pilot, I have a 10-12 hour flight coming up on May 2, but so far no one has taken an interest. Maybe no low-time pilot sees the value of flying left seat with a 2300-hour pilot at less than the helicopter’s operating cost. Whatever.

  2. Maria Langer :

    As for getting experience flying left seat with an experienced pilot

    I can vouch for the value of that kind of experience. A friend brought me along on a 1.2 hr ferry flight in his EC120. I learned nothing about flying the helicopter (it’s mostly like an R44 once you get it started), but so much about what I don’t know. Over the day and a half around that flight, I heard the phrase “Yeah, I know that’s what your CFI taught you, but…” at least a dozen times.

    I’m also going to guess that at least some of the CFIs you’ve flown with were taken aback by how different a revenue flight is from what flight training teaches you. For example, I’ve probably done about 10 approaches to the ramp without a trip through the pattern, and not one was during my flight training. The first few were ugly to the point of embarrassment. For me, flying the pattern was all part of getting in the mindset leading to the approach and landing, and not having that was disarming.

    p.s. If you pass through KPSC on the way up here, drop me a line. I’d offer to take you out to lunch but this place has very little to offer :(

    • Chris: Wanting to fly the pattern was the most obviously silly thing they did. Another was trying to avoid landing with a 4 mph tailwind. FOUR MPH! Three on board, light on fuel, less than 1000 feet DA. Sheesh. One guy would come in hot and make the spot with a quick stop — do that heavy in high DA and you’re gonna have a hard landing with a horn. I could go on and on.

      The problem is, most students learn within a 50 mile radius of their flight school and land at the same 4 – 8 airports all the time. No challenges at all. The guys I’ve flown with were sea level pilots operating in Seattle. They knew weather better than I did, but they didn’t know squat about operating in mountainous terrain or making last-minute changes to flight plans. It’s not their fault, though. It’s experience.

      And that’s the point. So many guys think, “I have 300 hours and can fly this thing. Why can’t I get a job now? Why do I need 1,000 hours?” It’s what you learn after you’ve finished training that gives you the experience you need to be a good pilot and make good decisions. What’s really unfortunate, though, is that most guys get the next 700 hours flying in the same 50-mile radius at the same 4-8 airports. What kind of experience is that?

  3. How about carb ice? 26 degrees C is 78.8 degrees F. Carb ice can occur between 25 F and 80 F, especially with the temp and dew point so close together, the mentioned high humidity condition. Low rotor rpm is a power thing not a flight maneuver thing (short of a power train failure). Rolling up the throttle could have compensated for the carb ice briefly until the continued/increased flow through the carburetor continued to add to the ice. Perhaps the correct response would have been to pull carb heat?

What do you think?