Posted on 04/13/2011 11:55:17 AM PDT by EveningStar
Newly released Federal Aviation Administration documents and audiotapes shed a scary new light on a bizarre incident late last year during which U.S. Senator James Inhofe landed his Cessna on a closed runway at a south Texas airport, scattering construction workers who ran for their lives as the politician’s plane hopscotched over them and six vehicles.
(Excerpt) Read more at thesmokinggun.com ...
Me too, but we can't run around with a Winchester and .45 on our hips though I have alway wanted to.
Perhaps it was the pilot's wings which were removed?
I’d know the Songbird’s engines anywhere!
didn’t Inhoffe lose the prop from his plane in the Clinton years?
But, this is a fairly common problem with Grumman Tigers due to the unusual spinner installation.
Maintenance-Related Accident
MS. CHARNON: Can you hear me? Okay. I don't know if this is going, but we're ready. All right.
Good afternoon. Like Dennis said, my name is Nicole Charnon, and it is my pleasure to be presenting you with a case study involving an in-flight separation of a propeller from the maintenance portion of this GA Symposium.
I'm going to start off this case study with an accident introduction, followed by our on-scene actions. I will then follow up with our Materials Laboratory findings, some supplemental type certificate and service difficulty reports that pertain to this matter.
I will follow or finish this presentation with some of our findings and then the NTSB's probable cause.
On May 8th, 1999, I received a call informing me that a Grumman AA-5B, otherwise known as a Grumman Tiger, had an in-flight separation of its propeller and was forced to make an emergency landing in Claremore, Oklahoma.
The pilot, who was a U.S. Senator, was flying his airplane from Ketchum, Oklahoma, to Oklahoma City, where he was to meet with the President of the United States to survey the destruction caused by one of the most severe tornadoes to hit the area just a few days prior to the accident.
The aircraft, November 4546 Juliette, was manufactured in 1979 by the Gulfstream American Corporation and had a 180-horsepower Lycoming 0-360-A4K engine installed.
The propeller that had separated was a two-blade fixed-pitch propeller, manufactured by Sensenich.
Once we arrived on scene, we interviewed the pilot, documented the accident site, and then examined the propeller and then moved the aircraft into a local hangar for the next day's examination.
During the interview with the pilot, he stated that while at 2,500 feet MSL, the airplane started to vibrate. He stated that the vibration worsened and soon the propeller separated from the engine, and the engine rpm exceeded its red line limits.
The pilot set up for an emergency landing in a field. However, after noticing his increased glide ratio, he elected instead to land at the Claremore Municipal Airport.
On final approach, the airplane started to porpoise. So, the pilot elected to land on the grass area next to the runway, and upon touchdown, the nose landing gear collapsed, the aircraft slid across the runway and came to rest as we see it here on its main landing gear and nose cowling.
Fortunately, for the investigation, the propeller assembly was located approximately three miles from the airport on a rural road and was brought over to the airport.
This is a photograph of the crankshaft flange at the accident site. As we documented the accident site, we noticed that the crankshaft flange remained intact. As we could see here, the entire propeller assembly and the starter ring gear are missing. The starter ring gear, however, was located approximately 60 feet from where the airplane came to rest.
The fractured propeller bolt ends were still installed on the flange's propeller mounting bushings and were fractured in the threaded section down inside the bushings, and I don't know if you can see here with this cursor. These are the bushings that I'm referring to around -- there's six of them around the crankshaft flange.
The Sensenich propeller assembly that had separated consisted of the following items. Number 9, we have the crankshaft flange with the six bushings. Number 8, we had the starter ring gear. We start the propeller assembly with Number 7, which is our aft spinner bulkhead, followed by the propeller spacer, the propeller, the forward bulkhead, a doubler, and then the spinner cone.
We examined the propeller assembly after it was brought to the airport. The Sensenich propeller assembly remained intact with the exception of six inches of propeller blade tip that was missing from one of its blades.
We later found that missing section of the propeller blade tip in the lower engine cowling and determined that as the propeller separated from the aircraft while still rotating at near cruise rpm, the one propeller blade sliced through the lower cowling, tearing off that six inches of blade tip, leaving it behind as the propeller assembly to the ground.
The propeller spinner cone, viewed here, displayed a puncture near its apex from the inside out. This is a view of the aft spinner bulkhead while still attached to the propeller assembly.
The aft spinner bulkhead displayed a peened or dimpled appearance. It also appeared that the propeller fell to and impacted the ground with the aft spinner bulkhead first, as you can see with the black asphalt marks here in this photo.
We concluded our first day of on-scene examination and started up the following morning. The next day, we examined the maintenance records and finished our on-scene examination of the aircraft.
Examination of the maintenance records revealed that the airplane's last annual was completed on 5/8/1998, exactly one year prior to the accident. The airplane's total time at the time of the accident was 1,734 hours.
On July 15th, 1983, the pilot had purchased a supplemental type certificate, otherwise known as an STC, to allow for the installation of a Sensenich propeller on the Grumman Tiger.
On October 27th, 1995, a new Sensenich propeller was installed on November 4546 Juliette. This was accomplished just 151 hours prior to the accident, and this was the last time this propeller assembly had been installed on this aircraft, according to the maintenance records.
After examining the airplane engine, cowling and maintenance records, we focused our attention back on the propeller assembly and removed the spinner cone.
All of the bolts remained with the propeller assembly, with the exception of one, which more than likely made that puncture hole near the spinner cone's apex as it departed the propeller assembly. Remnants of safety wire were still present on four of the bolt heads.
This is a photograph of the forward face of the aft spinner bulkhead. We noted at first what appeared to be elongated holes in the aft spinner bulkhead. As you can see, two of the holes, two of the six holes here, seemed to have relatively little damage, this one here, and this one up here, where the other four definitely displayed an elongated appearance.
This aft spinner bulkhead is going to play a pivotal role later on in this presentation. So, keep this photograph in mind for future reference.
The propeller assembly was then shipped to and examined at the NTSB Materials Laboratory here in Washington, D.C. During our examination, it was learned that the six propeller bolts failed as a result of fatigue cracking.
This is a close-up view of one of the propeller bushings with the fractured bolt still installed. As we could see here on this lower right side, we've got some good beach marks, indicative of fatigue fracture. All of the bolts displayed similar characteristics as this one.
We then examined the safety wire on our scanning electron microscope. You can see highlighted in this photo that magnification of the safety wire's flat fracture surface displayed fine striations which were typical of fatigue fracture.
The manufacturer specifications for hardness values and dimensions were then referenced, and all the bolts were found to be within those manufacturer specifications.
The bolt holes in the aft spinner bulkhead were examined. Four of the six bolt holes displayed a crescent-shaped sheared-off arc area. The elongation of the bolt holes appeared to be a result of being cut or punctured instead of being deformed into elongation.
There was a reason why two of the bolt holes did not display that sheared-off crescent-shaped area, which I will get into later on in the presentation.
Here's a close-up view of one of the aft spinner bulkheads bolt holes that have displayed the sheared-off crescent-shaped area highlighted here with the brace. As you can see, the metal around the hole had not been deformed into elongation but rather had been cut or punched out.
All the mating surfaces of the propeller assembly, including the crankshaft flange, the starter ring gear, the aft spinner bulkhead and the propeller spacer, displayed a severe peened appearance, indicating that the mating surfaces of the propeller assembly were subjected to considerable relative motion.
Up here in the upper left, we have the aft spinner bulkhead. On the upper right, we have the starter ring gear, and then on the lower left, we have the propeller spacer.
As we can see in all these photos, the peening damage that I talked about just a little bit ago on all the mating surfaces.
The STC used on the accident airplane instructed the mechanics to install the Sensenich propeller in accordance with the installation drawing provided by the STC and the manufacturer's service manual.
The Grumman Service Manual instructed the mechanic to temporarily secure the aft spinner bulkhead over the propeller mounting bushings during the assembly process.
A caution followed this instruction which warned the mechanics to the potential of damaging the aft spinner bulkhead if it was not held securely in place during the propeller assembly.
This is the installation illustration which was referenced in the STC. We have the crankshaft flange like I said before, with the six propeller mounting bushings. We have the starter ring gear which slides over top of those propeller mounting bushings and comes to rest against the crankshaft flange, and then we have the aft spinner bulkhead which also slides over the propeller mounting bushings and comes to rest against the starter ring gear.
This Number 7 here, this aft spinner bulkhead, is what the Grumman Service Manual is instructing the mechanic to temporarily secure during the propeller assembly process.
An additional STC, which also applied to the installation of the Sensenich propeller on the Grumman Tiger, is described here. It warns that the aft spinner bulkhead can slide off the propeller mounting bushings and come to rest against the bolts.
The mechanic does not detect that the aft spinner bulkhead has slid down against the bolts and continues on with the installation process. This particular STC recommended that someone either hold that aft spinner bulkhead in place or another option would be to replace two bushings with two longer bushings, so that they would be able to support the aft spinner bulkhead during the installation process.
We then searched the Service Difficulty Reports Database and found one report pertaining to this installation issue, and we can read here, it said that the aft spinner bulkhead was found with elongated mounting holes due to the crankshaft bushings not being long enough to support the bulkhead during installation. Mounting the bulkhead misaligned was causing cracking due to vibration.
The corrective procedures are illustrated above here on the left. This is a profile view of the propeller assembly and the crankshaft flange. Where is my cursor? There it is. Okay. We -- in white here, we have the crankshaft flange. In blue, we have the propeller mounting bushing. In red, we have the starter ring gear. In orange, we have the aft spinner bulkhead, and in white, the propeller spacer.
In front of that would be the propeller, and, of course, all this would be held together with the propeller bolt. Ideally, the aft spinner bulkhead would be temporarily secured over the propeller mounting bushings while the rest of the propeller assembly was being installed.
However, it appears that during the installation process, the aft spinner bulkhead is sliding off of the propeller mounting bushings and coming to rest against the propeller bolts, as we can see here on the illustration to the right.
We now have the aft spinner bulkhead resting against the bolt, and now we now have a space between the aft spinner bulkhead and the starter ring gear.
As illustrated on the drawing on the left, the mechanic continues with the installation process by torquing the propeller bolts and pinching the aft spinner bulkhead between the propeller mounting bushing and the propeller spacer.
Eventually, those crescent-shaped sheared-off arc areas are worn through the aft spinner bulkhead, and the propeller becomes loose. The propeller's bolts, of course, lose their torque. The propeller starts to vibrate, and eventually we have a fatigue fracture of the propeller bolts.
I explained earlier that four of the six aft spinner bulkheads bolt holes contained those crescent-shaped sheared-off arc areas, and that's because two of the propeller bushings are considerably shorter than the others, and that's for propeller indexing purposes during the installation process.
The remaining four longer bushings are really not all that long themselves because after we have this starter ring gear in place, we don't have enough propeller bushing to independently support that aft spinner bulkhead during the propeller assembly, and therefore it slides off and comes to rest on the bolts.
So, therefore we need a temporary means of securing that aft spinner bulkhead in place.
The problem is that most general aviation mechanics do not have reference to the maintenance manuals or the STC information and are not aware of this potential installation error.
The mechanics see this as a typical fixed-pitch two-bladed propeller and install it in the opposite manner in which it was disassembled. It is apparent that more than one mechanic has performed this installation error.
Both STC owners indicated that this is not an uncommon occurrence, and that they had found numerous aft spinner bulkheads with loose propellers due to the same issue.
The one STC owner estimated that nearly 40 percent of all the Grumman Tigers that pass through his shop have loose propellers because of this installation problem.
The owner of that particular STC owner sent the NTSB three exemplar aft spinner bulkheads and the FAA three additional aft spinner bulkheads that displayed similar characteristics as the one that we had found on this accident airplane.
This is a photo of the three exemplar bulkheads that were sent to me, and as we can see here on this close-up view of the aft spinner bulkhead, the bolt heads were damaged in a similar manner to November 4546 Juliette's. The bolt hole in this lower left corner still has that crescent-shaped arc that hasn't quite yet been punched out, where the one over here and up here has.
In some cases, not only were these bulkheads damaged once, but sometimes they were installed improperly two or three times as we could see in these other photos. It looks like this one's been punched out twice, and this one looks like it's been punched out maybe even three times.
Some of our findings on this particular accident was that the installation of this propeller seemed straightforward. However, it was not. Also, the maintenance manuals and STC information are generally not made available to the general aviation mechanic by their facility, and another problem is, is that the mechanics are not requesting or using the instructions that are provided to them.
The NTSB determined the probable cause of this accident to be the fatigue fracture of the propeller bolts resulting from the improper installation of the propeller assembly.
That concludes my case study. I brought along the accident propeller assembly and the three exemplar bulkheads for any of you who are interested in looking at it later.
He needs to get his license revoked.
Yup! A “Bamboo Bomber”
Cessna T-50 / UC-78 Bobcat
(Variants/Other Names: Crane 1A; AT-8; AT-17; C-78; JRC-1)
History: First flown in 1939, the Cessna T-50 was that company’s bid for a successful five-seat commercial transport typical of many other aircraft built in the late thirties. While the wings and tail unit were wood, the fuselage was a welded steel-tube design with fabric over wooden skinning. A low-wing cantilever monoplane, it featured a unique retractable tailwheel and wing trailing-edge flaps, both electrically actuated.
The need for a training plane to help pilots convert from single to twin-engine aircraft enabled Cessna to sell 550 aircraft for this purpose to Canada (Under the designation Crane), followed by 33 T-50’s to the U.S. Army Air Corps under the designation AT-8. In 1942, the USAAF felt the T-50s would work well as light personnel transports and for liaison/communication. 1,287 AT-17 Bobcats (later designated as UC-78s) were delivered and served in all theaters of war. Not to be outdone, the U.S. Navy in 1942-43 purchased 67 planes, which they designated JRC-1s, to ferry pilots between delivery ports and transport navy pilots to new duty stations. The T-50 served in these various roles for several years after the war. Over two dozen Bobcats still roam the skies of the USA, Canada, and Australia/New Zealand.
Nicknames: The Bamboo Bomber; Useless-78, The Wichita Wobbler; Brasshat; Double-Breasted Cub; Boxkite; Rhapsody in Glue; San Joaquin Beaufighter
Specifications (UC-78):
Engines: Two 245-hp Jacobs R-755-9 radial piston engines
Weight: Empty 3,500 lbs., Max Takeoff 5,700 lbs.
Wing Span: 41ft. 11in.
Length: 32ft. 9in.
Height: 9ft. 11in.
Performance:
Maximum Speed: 195 mph
Cruising Speed: 175 mph
Ceiling: 22,000 ft.
Range: 750 miles
Armament: None
Number Built: ~5400 of all models
Number Still Airworthy: ~25
Where’s Penny?
My father called it a Useless and said it was a female dog to fly.
FYI....it is not Hart's (or anybody's) Field.
It was name for the greatest Mayor in Atlanta history.... William B. Hartsfield
So Carters Field is a possibility looming huh?
He spoke truth to power continuously from the Senate floor.
I know how this sounds, but the truth is that many people met their deaths during the clinton reign of terror, over thrity associates of bill clinton. Most by drive-by shooting in out of the way places and quite a few, and I mean this is a huge coincidence, in small planes. Imhoffe took off once and very quickly his the propeller of his plane (whatever brand he was flying then), FELL OFF. Totally. He was able to land via his skill and probably luck. Interesting, too, the propeller was found. I never heard whether or not tampering was involved.
He flys from his home to areas around his huge state to visit citizens and attend various events.
No tampering, a bolt issue with the addition of a newer propeller.
Propellers separating are not commonplace, but more often than people realize. The MU-2 and anything with Garretts on them suffer catastrophic blade separation because the blade spins within inches of the fuselage.
Most fixed pitch blade separations take place after a reworked prop gets an overhaul - new twist after it had a ground strike.
Not a Beech 18
It’s a Cessna Bobcaat, AKA Bamboo Bomber, known to the Army Air Corps as the T-50 or U78.
The “Bamboo Bomber” was Cessna Aircraft Company’s first aircraft and made its first flight on March 26, 1939 with Dwane Wallace at the controls. Built with the standard steel tube frame and covered with fabric, plywood and aluminum, a cantilever wing of laminated spruce and powered by a pair of Jacobs R-755-9 7 cylindar unsupercharged air cooled radial engines producing 245hp at takeoff. It trued out at about 130 kts with 5 pax.
That’s not funny!
I read the actual report at the site and it sounds like the story is exaggerated. He was told to take a a remedial course, which he did.
Well, they probably were — I never got to fly one, and, FRankly, have no interest.
I have, OTOH, seen a few nice ones at airshows, and FRom an antique aircraft viewpoint, they are interesting and probably worth a nickle or two, due to their rarity.
I’d rather own and fly a P-51 or a P-47 though. Or maybe a Corsair or P-38.
If I had my druthers.
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