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Banner Towing, Dallas Redbird operation April 28, 2005 The Lycoming O-540 becomes an O-450 I was towing the giant 4,000 sq ft banner from 11:00-13:00 today with the "A" model short wing Pawnee. I tried to circle Downtown Dallas first, but the controller at DAL was too busy with departures (they were on south flow climbing out over downtown) so she told me "unable". No problem, I requested and received permission to fly north on Central Expressway (HWY 75). As soon as I was clear of the departure corridor for runway 13L at DAL, I started making left 360°'s over the major intersections on my way to the "High Five" (intersection of HWY 75 and HWY 635). Stuart - the boss - has told us many times that making money towing banners is all about circling over major intersections so everybody can see your advertisement. I orbited the "High Five" for about 20 minutes then requested permission from Addison Tower to proceed westbound on 635 to the Galleria Mall, which is also at the intersection of 635 and the Dallas North Tollway. Addison wasn't too busy so they approved my request and then I orbited the Galleria for about 20 minutes. It was at this time in my flight that I noticed something "different" in the sound of my motor. Every once-in-awhile, I would hear a strange popping sound. I started checking my magneto's but couldn't get the popping sound to stay with me 100% of the time, get better or get any worse. The popping noise would just come and go at random intervals. I discovered that if I pushed the power up to about 2,500 RPM the noise would go away. Needless to say I was just a tad concerned, but since my magnetos were operating normally and all the engine instruments were indicating that everything was normal I continued with the mission - besides, Addison airport was 4 miles to the north of me if something got worse. This went on for the 20 minutes I was over the Galleria and I finally got used to the sound since I could make it go away by applying power and everything seemed normal. It was a very gusty day so I just figured I was hearing the engine exhaust differently when the wind gusted across my airframe and blew the sound waves around differently. Since I was getting more relaxed, I flew back to the "High Five" and decided to see if things at DAL had calmed down enough for me to orbit downtown. Sure enough, I checked in with the DAL controller and received permission to enter Class "B" airspace and orbit downtown. The flight continued on - with my new intermittent nagging noise - until my time was up and I headed back to Redbird. RBD was landing to the south so I negotiated with the tower to drop my banner alongside RWY 17 in the grass between the runway and the parallel taxiway. The procedure is to hold 1,000AGL until over the airport boundary then reduce power and hold 60MPH until you are 300' above the ground, level off at 300AGL till over the target and then release your banner. When I pulled the power off to begin my descent, the whole airplane began to shake pretty bad - it was at this time I realized I had a serious problem with my motor. All engine instruments still indicated normal so I elected to proceed with a standard banner drop and then fly a TIGHT power off pattern to landing. Sure enough, after I released the banner and added power, the motor smoothed out. Anyways, the banner drop and subsequent climbout, circuit around the pattern and landing were uneventful - other than the shaking airplane when I pulled back on the power. I taxied back to the hangar, shut down and proceeded to do a little trouble shooting. Ensuring that everything was indeed turned OFF, I pulled the prop through by hand several rotations noting that after 5 strong compression strokes, what should be the 6th compression stroke was not there. I then turned the engine over with the starter with the ignition off and could hear a "SHHHH" sound out the exhaust pipe. I called the boss and informed him that I was putting a sign in the cockpit grounding the airplane and he and I decided to get the mechanic in the hangar next door involved with an official trouble shooting call. I had to drive out and roll up the banner and put everything away before the mechanic was able to come and check things out, but he was left instructions on his answering machine and we were assured by his assistant that he would be right on it. I returned to the airport the next day to fly a mission in Denton, TX - with the Hutch wing Pawnee that the boss had just brought us 4 days earlier. I noticed that there was a notepad and pen laying on the wing of the ill Pawnee. On the notepad was the mechanics notes of the compression check he had done the previous evening. 5 of the 6 cylinders registered in the low 70's over 80lbs of pressure - cylinder number 3 registered 9lb's over 80! I had been flying around with a 5 cylinder O-450 instead of a 6 cylinder O-540 engine for probably most of my flight the day before! Needless to say I learned a lesson from this - trust your instincts, if you think something is amiss, land and check it out! I am quite impressed with the Lycoming O-540 motor though since it held together without complaint (other than vibrating at low power settings) while dragging around an inoperative jug. |
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02/10 Training Begins | 03/22 Dallas Redbird Operation | 04/06 WWII Bombers Descend on RBD 04/26 The "Hutch" Pawnee | 04/28 O540 becomes O450 | 05/12 Ooops | 05/16 Traffic Watch Again |