Inappropriate Solo Training Landing Zone?

How about preventing accidents by making conditions easier for new pilots?

I stumbled across this brief preliminary accident report in the NTSB database today. Here it is in its entirety:

The pilot who held a commercial pilot certificate with single-engine land airplane ratings was receiving training to obtain a helicopter rating. The pilot had 31 hours of helicopter flight time and the accident occurred on his second solo flight. The pilot reported he was attempting to takeoff from a wet grass area when the accident occurred. He stated that when he increased the collective to lift off, the helicopter began to roll to the right with the right skid still on the ground. He moved the cyclic to the left and the helicopter responded by rolling to the left with the left skid contacting the ground. The pilot then applied right cyclic and the helicopter again rolled to the right. The right skid contacted the ground and the helicopter rolled over onto it’s right side. As a result of the accident, the main rotor blades and the helicopter fuselage were substantially damaged. The pilot reported that there were no preimpact mechanical failures/malfunctions that would have precluded normal operation.

The accident aircraft was a 2003 Robinson R44 Raven II.

Those of us who have soloed in Robinson (or other small) helicopters know that balance varies greatly depending on how many people are on board. We learn to fly helicopters with two people on board: student pilot and instructor. The helicopter is usually quite balanced with two people on board. I don’t have the exact numbers for this particular flight, but using my R44 as a guide and assuming the pilot and instructor were each 200 pounds with 1/2 tanks of fuel, the weight and balance envelopes should look something like this:

W&B with 2 On Board

If you’ve never seen one of these, let me explain. The longitudinal weight and balance chart shows where the weight is distributed front to back. The pink line represents the main rotor mast. With two 200-pound people on board in the front seat, the center of gravity is forward of the mast. This is pretty normal for an R44. The lateral weight and balance chart, which is what we’re more concerned with in this analysis, shows how the weight is distributed side to side. The 0.00 mark is dead center and, as you can see, the with/without fuel points are very close to the center. In other words, it’s laterally quite balanced.

Now take the instructor out of the left seat. With everything else remaining equal, here’s what the weight and balance envelopes look like:

W&B with 1 on board

First of all, the center of gravity shifts aft. That makes a lot of sense. After all, there’s 200 pounds less weight up front. When I fly, this is extremely noticeable, especially at my new, slimmer weight. The helicopter actually lands on the rear of its skids first; on pick up, the front of the skids come off the ground first.

Laterally, there’s also a big change — and again, that’s what we need to focus on here. Without that 200 pounds of weight on the left side of the aircraft, the center of gravity shifts quite a bit to the right. The heavier the pilot is, the more to the right the weight shifts. So although I used 200 pounds in my example, if the pilot was 250 pounds — which is still legal in an R44 — the weight would shift even further to the right (and slightly forward). When the pilot attempted to lift off, the left skid would rise first.

Again, I don’t have the exact numbers. You can play with this using any reasonable numbers you want. It won’t change the conclusion here.

Now read the description of the accident events and put yourself into the pilot’s seat. He’s taking off so he’s lifting the collective slowly, getting the helicopter light on its skids. The left skid comes off the ground first because that side of the aircraft is lighter. This feels to the pilot as if the helicopter is rolling to the right while the right skid is still on the ground.

Stop right there. This is where the terrain comes into the picture.

The pilot is on wet grass. The accident report didn’t say mud so we won’t assume a sticky surface. But it certainly isn’t smooth. We don’t know how long the grass is or whether it’s uniform or has clumps of thick weeds. The question we should be asking is this: was the right skid “stuck” and creating a pivot point? The answer to that question determines the appropriate action:

  • If the right skid is indeed “stuck” and creating a pivot point, the correct action to avoid dynamic rollover would be to lower the collective. In other words, abort the pick up.
  • If the right skid was not “stuck” or creating a pivot point, the correct action would be to adjust the cyclic to assure there was no lateral movement (as you’d normally do in a pick up) and continue raising the collective.

An experienced pilot would know this. An experienced pilot would have done dozens or hundreds or thousands of solo pickups. He’d have a feel for the aircraft or, at least an idea of what to expect and what to do.

But this wasn’t an experienced pilot. It was a student pilot with only 31 hours of flight time — almost all of which was with a flight instructor beside him — on his second solo flight. So he used the cyclic to stop what he perceived as a roll. He may have been more aggressive than he needed to be, thus causing the helicopter to come down on the left skid. Then another adjustment to the right. The right skid hits that grassy surface and the helicopter rolls. Game over.

So my question is: What the hell was he doing taking off and landing on wet grass?

Flight instructors can reduce the chances of accidents like this by setting up their student pilot solo flights with easy flight conditions. That includes smooth surfaces for takeoff and landing. If this had happened on a nicely paved airport ramp or helipad that was free of surface obstructions like cracks or tie-downs, this accident may not have happened at all. There would be no question about a pivot point because none could exist.

You might also question whether the flight instructor properly taught the concept of dynamic rollover and what to do if it’s suspected on takeoff — lower the collective. And whether the flight instructor made it clear that there should be no lateral movement on pick up or set down. Yes, I know that’s hard for a new pilot to do — especially with only 31 hours — but it’s vitally important, especially on surfaces that could snag a skid.

Which brings me back to my original point: why was he taking off from wet grass?

Fortunately, the pilot was not injured, although the helicopter was substantially damaged. I think this accident makes a good example for teaching about dynamic rollover. With luck, instructors and students will learn from the mistakes here and avoid them in their own training experiences.

Of course, another possibility is the the student pilot simply was not ready to solo.

6 thoughts on “Inappropriate Solo Training Landing Zone?

  1. Interesting, but with quite a few assumptions. Do you know the weight of the pilot the fuel load, and actual cg of the aircraft in question? Was there a slope in the takeoff area? What was the relative wind in the takeoff area? Maybe it was a slope. Maybe he just over-controlled.

    It would be nice to take all the risk out of flying, but there is just an inherent risk. It was a helicopter and it was on wet grass; not a real stretch for a helicopter, even one being flown by a student.

    Look, he has some flight skills, he already had a fixed wing license. Sure, it could have been dynamic rollover but that seems a stretch.

    All I’m saying is that it could have simply been a pilot ham fisting the controls rather than an instructor failure, exceeding critical tilt, or some other abnormality. Your analysis is thoughtful, but the old fart in me makes me think he might have just did it to himself…

    • As far as “assumptions” go, I did say at least twice in the post that I did not have exact numbers. Perhaps you missed those paragraphs? I also said that any numbers used in the calculation will show the same results: CG is shifted to the right with only one person on board.

      I can make further assumptions. For example, I can assume that the student pilot was a big guy — more than 200 pounds — because he’s training in an R44, which costs about twice as much per hour dual than an R22. Unless the helicopter was his, why would he train in a more expensive ship? That means the CG is likely to be shifted even more to the right. Of course, I could be wrong — this is just another assumption. But does it really matter? Any numbers entered will tell the same story.

      You cannot compare airplane flight skills to helicopter flight skills when it comes to taking off (picking up) or landing (setting down). Those skills simply do not translate. I’m thinking that to suggest this, you are probably not a helicopter pilot. I don’t know a single helicopter pilot — or at least an experienced or well-trained one — who would suggest that airplane skills are useful when lifting a helicopter off the ground.

      And when you say “sure, it could have been dynamic rollover” — well, that just confirms my suspicion. Could have been? It was dynamic rollover. What happened is the definition of dynamic rollover: the helicopter rolling over a pivot point (the right skid, in this example). From the report:

      The right skid contacted the ground and the helicopter rolled over onto it’s right side.

      Identifying this as dynamic rollover isn’t “a stretch.” This is the definition of dynamic rollover. Here’s some extra reading material on the topic in Wikipedia: http://en.wikipedia.org/wiki/Dynamic_rollover

      Frankly, I agree that the student pilot probably “ham fisted” the controls, likely because of his lack of experience. But I don’t want to place blame solely on him if he was set up in a bad training environment. I’ll stand by my original statement: a student pilot on his second solo flight should not be lifting off from a wet grass landing zone. If the instructor set this up, the instructor needs to take some of the blame for what happened.

      I do want to point out one thing that was not mentioned in the report: did the instructor approve the LZ? We’ve all heard stories about solo student pilots showing off to friends and family members by landing off airport. Perhaps this is what happened? The student landed at an unapproved landing zone during that flight? Not sure if we’ll find out; the NTSB doesn’t always investigate or report as thoroughly when there isn’t a fatality or serious injury.

  2. Interestingly enough, the NTSB already created their docket for this accident. I mentioned it to you last time as a way to get a little more info on investigations. From the docket, we are given Max Gross of 2500lbs and weight at time of accident at 1974lbs. Center of Gravity is given at 99.12 from the datum, but does not include the lateral CG. From reading the pilot’s narrative, I get the impression that he was unused to the feel of the helicopter without an instructor, and over-controlled the machine during the pickup resulting in the dynamic rollover.

    From the pilot:
    “As I got ready to lift off I set the cyclic to the left and slightly forward of the position used for take-off with the instructor on board. This was successful in the morning except the machine started moving forward on that departure so I used less “forward” this time.”

    From the instructor who was watching:
    “As the aircraft was coming off, the ground I noticed that he
    was leaning to the right he over overcorrected and was in an unstable hover. The aircraft then started a
    rolling moment to the right, as there was the right skid creating his pivot point.”

    • I remember you mentioning dockets, but forgot to look this one up. Surprised they didn’t calculate lateral CG; I think it’s important here. The pilot definitely over-controlled — how else would you describe bouncing from skid to skid? But I still think the grass was a factor in the rollover.

  3. I really enjoy reading your blog. I am currently in flight training to be a helicopter pilot and have gained a lot of knowledge from your writings. Can you provide a link for where you go to read the NTSB reports?

    • Thanks! And sure: go to http://www.ntsb.gov/ and click on the Aviation Accident Database icon. That’ll take you to the Query page, where you can search for accidents based on a number of criteria. I usually search by date (say, for the past year if I’m browsing) and select Helicopter as the Category. If I’m looking for a specific accident and don’t have the NTSB number, I’ll put in a range of dates near the accident date and provide as much info as I can — for example Category = Helicopter and State = Washington.

      I should probably blog about how I do my searches. Thanks for asking; it would make a good topic for a brief post.

What do you think?