Inside the Wasp Shop with the Aeroshell Aerobatic Team & Covington Aircraft

Gene McNeely started flying airshows in 1986 and has been a stalwart presence on the AeroShell aerobatic team, flying a Wasp-powered North American T-6. He can only guess at his total flying time behind the engine: “I would say 15,000 hours…probably more than that.” He does remember exactly how he got there, though. “I got out of the Navy and…started cropdusting, and the first engine I sat behind was the [Pratt &Whitney] R-985, which we’d adapted to the Stearman,” he recalls.

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Radial Engine Cylinder Head Checks: Following the Service Bulletins

This is the seventh and final topic in the series about the 100 hour / annual inspection. This series focuses on maintenance performed during an effective 100 hr. inspection on R1340 and R985 engines:

  1. Oil Change with filter/screen & sump checks.
  2. Valve adjustment – Positive or compression.
  3. Ignition timing check – Spark plug servicing.
  4. Compression check – differential.
  5. Air filter and carb – heat system check.
  6. Fuel System Screens.
  7. Cylinder Head Checks.

It has been amazing to see the engine log books for both the R-985 and R-1340 engine cores coming back to us for overhaul with not one entry reflecting the visual inspections called for in Airworthiness Directive 78-08-07 (R-985-SB 1785) and AD # 99-11-02 (R-1340-SB 1787)!

The service bulletins outline an Ultrasonic inspection of the 985 cylinder heads and Florescent Penetrant inspection of the 1340 heads that must be done at each overhaul. However, there are instructions for visual inspections to be done on the cylinder heads of both engines at specific intervals! The AD Note 78-08-07 (985) stipulates visual inspection of the heads on a 150 hour interval while AD 99-11-02 (1340) states inspections must be done on a 100 hour basis!

The AD notes state the inspections must be done in accordance with the SB’s. SB 1785 which reads as follows: REASON FOR BULLETIN: (2) Provide instruction for visual inspection, at each periodic maintenance interval. The 1340 SB reads: REASON FOR BULLETIN: 3. Provide instructions for inspection of cylinder heads at periodic maintenance.

You are looking for cracks in the aluminum head that are evidenced by jet-black combustion residue deposited at the root area between two fins in the designated areas. The coloration will not be visible in areas that aren’t cracked and leaking combustion residue. It is possible for oil leaks to burn onto the cylinder cooling fins but that is usually dark brown colored and typically involves a larger portion of the head. Combustion residue is dark black and may be oily and gritty feeling. I have included a couple of scanned illustrations showing the areas of the head identified in the bulletins:

radial engine cylinder head checks

The pictures seem to indicate that the 1340 head doesn’t experience cracking around the side of the head and that the 985 doesn’t crack across the top. However, cylinders of both the R-985 and R-1340 engine can develop cracks in either location on the heads!

Some careful reviews of the requirements are in order due to the confusing wording of the AD notes vs SB’s!

R-985: The AD affecting the 985 states: “To prevent cylinder head separation from the barrel, perform the following in accordance with Pratt & Whitney Aircraft Service Bulletin No. 1785 or later FAA-approved revision.” (Paragraph) 1. “Visually inspect cylinder heads in accordance with Part B of the bulletin as follows: (Sub-paragraph) B. “Cylinders Ultrasonically inspected, inspect within 150 hours time in service after effective date of the AD, and thereafter at intervals not to exceed 150 hours time in service.”

Service Bulletin 1785 references the R-985 Wasp Jr. Engine Maintenance Manual, Part No. 118611; Periodic Inspection. That inspection table places the check of the rear of the cylinder head for cracks or evidence of exhaust gas leakage in column “B”; 100 hours! To correctly comply with the AD the 985 cylinder heads must be visually inspected on a 100 hour basis!

R-1340: The 1340 AD and Service Bulletin are no less confusing! The AD instructs the mechanic to inspect the cylinders in accordance with SB 1787 dated September 07, 1983. However, the AD states that cowled and baffled installations should have an initial inspection at 125 hours and subsequent inspections at 250 hour time in service since last inspection. All other installations (translates “Cropdusters”) are to have an initial inspection at 50 hours and subsequent inspections at 100 hours! The SB allows for cowled and baffled engines to be inspected at 500 hours and un-baffled or “cropduster” type installations at 200 hour intervals. Sadly, the AD note is the law! You get to inspect using the technique given in the respective SB and accomplish the inspection at the intervals specified in the AD! Oh well, what do you want? Good looks and money too!

By the way; if it isn’t written in the log book, it didn’t get done!

We hope you have learned a few things from this series!

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A Flying Swiss Army Knife: The Many Faces Of The Pilatus PC–6 Porter

It’s a missionary and a mercenary. A soldier and a spy. A record-setter and an also-ran. After 60 years of continuous production, the Pilatus PC–6 Porter, a legendary Swiss turboprop that has played more supporting roles than Kevin Bacon, will cease production in 2019.

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The TBM 700 Powered by the PT6A-64 Led to Even Faster TBM Variants

The SOCATA TBM (now Daher TBM) is a family of high-performance single-engine turboprop light business and utility aircraft manufactured by Daher. It was originally collaboratively developed between the American Mooney Airplane Company and French light aircraft manufacturer SOCATA.

The design of the TBM family originates from the Mooney 301, a comparatively low-powered and smaller prototype Mooney developed in the early 1980s. Following Mooney’s acquisition by French owners, Mooney and SOCATA held a series of in-depth discussions on the potential for co-developing a new enlarged turboprop design derived from the earlier 301; these resulted in the formation of a joint venture for the purpose of developing and manufacturing the envisioned aircraft, which was designated as the TBM 700. From the onset, the emphasis was placed upon the design’s speed, altitude, and reliability. Upon its entry into the market in 1990, it held the distinction of being the first high-performance single-engine passenger/cargo aircraft to enter production.[

Shortly after launch, the TBM 700 was a market success, which quickly led to the production of multiple variants and improved models, often incorporating more powerful engines and new avionics, amongst other features. 

The prefix of the designation, TBM, originated from the initials “TB”, which stands for Tarbes, the French city in which SOCATA is located, while the “M” stands for Mooney. At the time of its conception, while several aviation companies had studied or been otherwise considering the development of such an aircraft, the envisioned TBM 700 was the first high-performance single-engine passenger/cargo aircraft to enter production. From the onset, key performance criteria were established for the design, demanding a high level of reliability while also being capable of an unequaled speed/altitude combination amongst the TBM 700 other single-engined peers.

The Pratt & Whitney CanadaPT6A-64 engine, providing up to 700 shp (522 kW) powers the TBM 700. According to Flying Magazine, the PT6A-64 engine is “the secret to the TBM 700’s performance. At sea level, the engine is capable of generating a maximum 1,583 shp (1,180 kW), which is intentionally limited to 700 shp (522 kW) on early TBM models; the limit allows the aircraft to maintain 700 shp (522 kW) up to 25,000 ft (7,620 m) on a typical day. Engine reliability and expected lifespan are also enhanced by the limitation. While the typical engine overhaul life is set as 3,000 flight hours between overhauls, on-condition servicing can also be performed due to various engine parameters being automatically recorded by the engine trend monitoring (ETM) system. Data from the ETM can be reviewed by the engine manufacturer to determine the level of wear and therefore the need for inspection or overhaul. The ETM, which is connected to the aircraft’s air data computer, also provides information to enable easy power management by the pilot.

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The Douglas DC-3: 85 Years and Going Strong

The Douglas DC-3 Doesn’t Know the Meaning of the Word “Quit”

The same year the German airship Hindenburg crossed the Atlantic, the still-flying-today Douglas DC-3 was introduced to the world. The DC-3 is widely viewed as one of the most significant transport aircraft in history, due to its massive and long-lasting impact on the airline industry, and aerospace engineering. I got the chance to interview Ric Hallquist, the retired Chief DC-3 Pilot for Missionary Flights International who flew and worked on the beefy twin engine transport plane for over 30 years.

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