A Pilot's Perspective.

By Barry Meek.

February 2011   

Honey, We've Lost the Prop!...

(A true, in-flight emergency)

AN ENGINE FAILURE while in flight is every pilot's nightmare.  Losing a prop, although the result is the same, can be way more traumatic as structural damage may occur, rendering the aircraft uncontrollable.  In 2006, the wooden prop on Marc Zeitlin's COZY MKIV departed the aircraft while flying over a California desert.  One of the tips was found embedded in a wing tip, but fortunately no control loss was experienced. 

Still, Marc was faced with landing a rather fragile, high-performance airplane, without power, in the middle of a desert wilderness.  He did everything right, his airplane survived virtually intact.  More importantly, he and his wife are alive today to share the tale.  Told in his words, here is that story.

BANG!  Deanie said "Oh my god - what was that?"

 "I'm not sure".  I brought the throttle back, noticed that the aircraft vibration had almost completely disappeared, and that we had started descending and slowing.  I pushed the throttle back in.  The RPM went up but there was no change in vibration and there no thrust from the prop.

 

"I think we lost the prop.  The propeller came off the engine". 

Deanie said, "Oh my god - what are we going to do?"

 "We're going to land".

I slowed us down to Best Glide speed and punched the "Nearest" button on the GPS.  It told me that Desert Center (L64) was 17 NM almost directly ahead of us.  We were at 9500 ft., it was at ~500 ft. ASL, and there were no hills/mountains in the way.   We also had about a 15 kt. tailwind.  A quick calculation of glide range determined that we should get there with at least 1000 ft. to spare over the pattern altitude of 1500 ft.  At some point in there I must have turned off the autopilot to follow the GPS to L64, but I don't remember doing it.  All this took about 15 - 30 seconds.

Deanie was asking if I was going to call ATC.  I said I'd talk to them when I got a chance. Aviate, navigate, communicate.

I spent the next 30 seconds playing with the throttle and the controls to try to understand what had happened and how the plane was doing. Everything seemed to be working - the engine was running, the numbers on the gauges were good, and the plane was flying fine.  We were at 100 mph, descending at about 600 fpm.  No thrust, though - although I couldn't see the prop arc (or lack of it), I was pretty convinced that the prop was gone.

Deanie was very upset, but she was holding herself together and letting me do what I had to do.  I spent a few seconds every minute or so telling her that everything was OK - the plane was flying, and we were going to land at an airport. 

After a minute or two, I felt stable enough to get on the radio.  I tuned in 121.5 and said "Mayday, Mayday, COZY N83MZ is 15 miles northwest of Desert Center at 8500 ft. with engine trouble.  We're going to land at Desert Center".  An aircraft replied (commercial jet, I believe) and relayed our call to LA Center, who then responded to us.  They got all our info and had us squawk 7700.   They asked for Souls on Board and our intentions, and I told them that I believed that we could make it to L64 and land there.

Although I had asked Deanie to look at the chart and give me the field elevation, runway length, and CTAF for L64 (more to give her something to do than anything else), ATC read me the info too.  I dug out a pen and Deanie wrote down LA Center's phone number - they asked me to call them when we were on the ground to let them know we were safe. 

We were getting closer to L64 (and lower, obviously), and although I could see Interstate 10 to the south, I was having a little trouble finding Desert Center.  Deanie was still very nervous and shaking, and I kept telling her that everything was fine, we were just going to make a normal landing.  I found the strip, picked a landing direction, and we arrived over the field at about 3500 ft. - 2000 ft. to spare. Since we were high and had the field made, I put the nose gear down so I wouldn't have to think about it anymore.

Deanie was already nervous enough, so I explained we would come in high and I might have to slip to get down, so if we get a bit sideways, it's on purpose and OK.  She knows what a slip is.  I did a standard left pattern for runway 23, albeit high, so I kept it a little wide.  As I turned base I thought I was still high.  I put the landing brake down, but after about 10 seconds and turning final, I brought it back up.  There was a touch of crosswind, but other than that it was a completely normal approach and landing.  We touched down about 1000 ft. down the 4200 ft. runway and I rolled to the end and off onto the single taxiway.

We were on the ground and safe.  From the time of the "BANG!" to rolling to a stop, we had been in the air for approximately 12-13 minutes.  Things happened slowly - there was time to think, time to evaluate, time to react, and time to decide.

We unbuckled and hugged for a couple of minutes - I told Deanie that everything was OK - we were safe, unhurt and on the ground (albeit pretty much dead center in the middle of nowhere).  That was all that mattered.  

I got out of the plane and called ATC to tell them we were on the ground and safe, and to thank them for their help.

I then gave the plane a once over.  Checking the engine, my suspicion was correct - everything aft of the prop was gone.  No spinner, no crush plate, no prop blades, no prop hub - nada, zip, zilch, zero, nothing.  All six prop bolts had broken at the base of the threaded portion deep within the extension bushings.  The threads were all still in place in the bushings.

One bushing was substantially deformed as the bolt tore out - it must have been the last bolt to go.  A cursory view inside the cowl didn't indicate any major damage.

As I was marveling at this - the forces required to tear prop bolt completely off, I happened to look down the wing at the right winglet. I was greeted by the view of a missing lower winglet, as well as a chunk torn off the trailing edge of the wing (and a tiny corner of the aileron).  As the prop departed, it apparently took about 80% of the right lower winglet with it. The blade had torn off the trailing edge of the wing just  behind the rudder cable conduit - 1/2" further forward and I wouldn't have had a working rudder on the right side.

I took the top cowl off - as far as I could tell, there was essentially no damage.  Nothing shook loose, nothing cracked, nothing moved.  I spent some time evaluating the wingtip damage as well - we had flown for 13 minutes like that, and I had no inkling from the aircraft's performance or behavior that anything was wrong. 

Cause:

While my original theory was that a blade broke, I'm now 99.99% convinced that it was a  prop bolt torque issue.  My big error in judgment was in not landing at Twentynine Palms, where there's an FBO, a town, and which we were right over when the problem manifested itself. (Well before the big BANG, there were several periods of small vibrations in the aircraft, corrected by adjusting the power.  ed.) The decision to continue on and land at Blythe was stupid, and could have cost us far more than a lost day and an airplane parked in the middle of nowhere.  Deanie has tried to make me feel better about it by saying that we might have landed, found nothing, and then had the prop disappear as we were taking off, which would have been worse.

Maybe so, but far more likely is that by that time the problem was large enough so that I would find something and ground the plane in civilization, with an intact wing and winglet (and prop extension and spinner).

But I'll never know.

For the longer, original description of this incident, you can go to:  Marc Zeitlin's website http://www.cozybuilders.org/

Story and pictures copyright :  Marc Zeitlin.   Used with permission.

The communication between ANOTHER pilot in trouble and ATC can be heard here:

http://www.funplacestofly.com/blog.asp?ID=305     This is worth listening to!

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