Saturday, June 6, 2015

The Night The Ground Came Up



My previous post, "Geronimo!" got me thinking fondly of N2064P.  Though Jere and I only flew a few flights in her, both he and the Chief Pilot of the school now had a confidence in my ability to fly the Geronimo safely.  In fact, in time, it led to opportunities to fly other light twins.  Jere kept her on our flight line, hoping for some rental revenue.  I rented her myself when I could.  There was one trip out to Henderson, Texas when I took my father on a business trip.  It has been said that pilots run through four distinct stages when acquiring a new skill set.  The first stage is "Intimidated", the second, "Cautiously Confident", the third, "Cocky", until something bad happens and then we are back to, "Intimidated".

It is true, I was growing out of the "Cautiously Confident" stage as the Geronimo and I were becoming good friends.  I learned a hard and valuable lesson one clear night in October, 1987 and the Geronimo was my teacher.  While I didn't quite bounce all the way back to "Intimidated", it was humbling.  Our flight school had arranged a maintenance program with a mechanic on Luck Field, an airport on the south side of Ft. Worth.  Luck Field is how it is listed in my logbook however, I cannot find it on a current chart, so it must have changed names or succumbed to land development, a fate many delightful airports suffer.  We had a Cessna-152 over at Luck which was ready for pick-up.  My fellow flight instructor, Mike, and I flew over there in the Geronimo and Mike got out to fly back in the 152.  It was late and I was in a hurry to get back to Redbird and home.  So, as soon as Mike slammed the door shut and I latched it, I was taxiing for take-off.  A few minutes later I was cruising at 2000 feet above ground level and all was right in the world.

Piper aircraft have a unique door system.  They almost always have just one door on the passenger side which open outward.  The top of the door necessarily follows the contour of the fuselage, thus curves in, giving it a clam shell look.  There are two latches, the main one located low and a secondary latch located up high above the curve.  Failure to secure both of these latches properly results in the door popping open and a lot of ambient noise.  Anyone who has flown Pipers long enough will experience one or more of these sudden door openings and they will notice two things right away, firstly, the door cannot be closed.  The slip stream follows the Venturi law and creates far more suction on the door than one can overcome and the door stubbornly trails about three inches open, and secondly, the plane will fly just fine, in spite of the fact that the trailing door creates a turbulent airflow across the horizontal stabilizer and elevator.  The main aggravation lies in the fact that to close the door and resume relative peace, a landing and another take-off is required.

Piper Arrow with open door

I had just leveled off and was heading east, when "PHWOOSH!" the door popped open.  I instantly realized what the noise was about and for the first moment I was simply annoyed.  However, in another moment I realized that I had a serious problem.  When the door came open the airplane started to descend.  This descent was happening at a rate of about 250 feet per minute and was occurring in spite of my having the yoke pulled all the way back, against the stop.  Quick mental calculations came up with several disappointing conclusions, namely that I wasn't going to get the door closed, I could no longer stay in the air and I wasn't going to make Redbird airport.  Ahead and to my left was the Grand Prairie airport and to my right was the Arlington airport.  Arlington had a little longer runway and I figured that the wind favored landing south, so Arlington it was.  I was relieved upon lowering the landing gear to note that my control ability was no worse with the configuration change.  I was unable to let go of the yoke long enough to look up the proper Common Traffic Advisory Frequency, the radio frequency with which I would be able to alert other airplanes near Arlington of my predicament and intentions.  I lit up every light I had and aimed for the runway knowing that this first approach would be the only possible approach.  I didn't risk using flaps, fearing that the nose down tendency would only get worse.  If anyone had been near enough to the runway to see that landing, they would have judged it to be a really poor one.  With the nose low and a little excess speed the airplane hit on the nose wheel first.  That popped the nose up and began a cycle of hitting the nose...the mains...airborne...nose...mains...airborne...nose...mains... with each cycle getting shorter and less pronounced and me holding the yoke back against the stop the whole way.  Finally, the old Geronimo was rolling down the runway in a normal fashion.  If you have ever heard of "knees going weak" following a stressful event, I can tell you that it's true.  I could barely stand up after crawling out of the cockpit. 



There was a period of time after that event wherein I was confused on why things went so wrong with a simple door pop-open.  Soon, upon calmer reflection I figured it out.  An airplane lives and dies by it's weight and balance.  In flight, with the center of gravity in the proper limits, the wing holds up the craft while the horizontal stabilizer provides a balancing downward force.  The elevators provide the modulation of that downward force to give the pilot his range of pitch attitudes, up and down.  An improperly loaded airplane will have one of those ranges limited.  In my case, I was alone in a four seat airplane and the CG was probably too far forward, thus requiring nearly all of my up elevator travel to maintain level flight.  When the door popped, the resulting turbulent airflow across my right elevator reduced it's efficiency causing my pitch attitude to re-balance slightly negative and down we went.

The FAA describes the accident sequence as a chain of errors, which individually are harmless, but when linked in series are catastrophic.  My failure to calculate an accurate weight and balance for this solo flight coupled with failing to latch the door securely set up the event.  Having a place to land, thankfully, broke the chain.  This was a huge lesson as I moved from the single engines to more complex aircraft.  The loading options in the single engines are limited and one learns what works without having to go through the trouble of a complete computation.  Computing the weight and balance used to be a pencil and paper affair requiring numerous adding, multiplying and dividing steps.  Today, a smart-phone app could do it in a few seconds.  I learned to slow down and meticulously complete each step of flight planning from this night when the ground came up.

No comments:

Post a Comment