Category Archives: radial engine

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!

Share and Enjoy

  • Facebook
  • Twitter
  • Delicious
  • LinkedIn
  • StumbleUpon
  • Add to favorites
  • Email
  • RSS

Importance of Fuel System Screens on your Radial Engine

This is the sixth 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.

Continue reading Importance of Fuel System Screens on your Radial Engine

Share and Enjoy

  • Facebook
  • Twitter
  • Delicious
  • LinkedIn
  • StumbleUpon
  • Add to favorites
  • Email
  • RSS

Air Filter & Carb – Heat System Check – The 100 hour Radial Engine Annual Inspection Series

This is the fifth 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.

Continue reading Air Filter & Carb – Heat System Check – The 100 hour Radial Engine Annual Inspection Series

Share and Enjoy

  • Facebook
  • Twitter
  • Delicious
  • LinkedIn
  • StumbleUpon
  • Add to favorites
  • Email
  • RSS

The 100 hour Radial Engine Annual Inspection Series – Compression Check

This is the fourth 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.

Continue reading The 100 hour Radial Engine Annual Inspection Series – Compression Check

Share and Enjoy

  • Facebook
  • Twitter
  • Delicious
  • LinkedIn
  • StumbleUpon
  • Add to favorites
  • Email
  • RSS

The 100 hour Radial Engine Annual Inspection Series – Valve Adjustments

This is the second 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.

Continue reading The 100 hour Radial Engine Annual Inspection Series – Valve Adjustments

Share and Enjoy

  • Facebook
  • Twitter
  • Delicious
  • LinkedIn
  • StumbleUpon
  • Add to favorites
  • Email
  • RSS

The 100 hour Radial Engine Annual Inspection Series – Part 1

It’s annual inspection season again. I guess it like death and taxes…sure to come around. Lots of folks have asked “what should I have done to my engine during the annual?” The engine maintenance manual, part number 118611 contains the Periodic Inspection Tables listing the Requirements for the “A” (50 hr), “B” (100 hour inspection), “C” (200 hour) and “D” (Midway to Overhaul) inspections on R1340 and R985 engines. Of the requirements listed I’d like to offer some recommendations on seven of the “heavyweights”.

Continue reading The 100 hour Radial Engine Annual Inspection Series – Part 1

Share and Enjoy

  • Facebook
  • Twitter
  • Delicious
  • LinkedIn
  • StumbleUpon
  • Add to favorites
  • Email
  • RSS

Radial Engine Operation Techniques That Can Shorten Cylinder Life

There are a number of Radial Engine Operation techniques that can shorten cylinder life (head failure). There are also a few mechanical problems that can cause premature cylinder head failure. The following items, hopefully, will shed some light on the subject.howmanyenginesdoyoucount

Continue reading Radial Engine Operation Techniques That Can Shorten Cylinder Life

Share and Enjoy

  • Facebook
  • Twitter
  • Delicious
  • LinkedIn
  • StumbleUpon
  • Add to favorites
  • Email
  • RSS

How 2 R-985s Aided the PT6 in Achieving Legendary Aviation Status

pt6a king airThe question of how a radial engine can be compared to a turbine engine is a question that has been asked many times over. Individuals in the Agricultural world are still asking themselves this question every year on a purely economic basis. However, the question can also be asked from a historic basis as well. In looking at the Pratt & Whitney family of Radial Engines and the PT6A family of engines, it is clear that the two are closely related.

A Bit of Background on Pratt & Whitney’s Engine Marvels: The PT6A, R-1340, & The R-985

A legendary engine deserves a story as extraordinary as it is, and such is the case with the early history of Pratt & Whitney’s PT6. This story begins decades before the turbulent history of the PT6 when radial engines were still the dominant engine for airplane use. The gas turbine engine of the PT6 revolutionized the industry, but not before the static, air-cooled radial engines had a few decades in the limelight.

Of all the radial engines, Pratt & Whitney’s R-985 was always a favorite since its inception in 1932. Simply sit back and watch a smile cross an aviation enthusiast’s face upon observing the sputter of the round radial engine as it starts up, and it is clear that these engines were something special.

However, the transition into the era of the PT6 was not an easy one. In fact, it was something of a miracle.

The Rise of the PT6

While the advancements of gas turbine engines were known to the aviation industry in the early 1950s, the expenses of the manufacturing, maintenance and repairing processes were problematic. However, that did not deter Pratt & Whitney Canada (PWC) while they forged ahead with their plans of designing a powerful gas turbine engine. They hired a team of specialists and proceeded with attempts to develop a 450 hp engine that had growth potential up to 500 hp. Their goal was to keep operating costs at a similar level as the previous radial engines, and their first foray into gas turbine engines was designed to fit small and lightweight airplane models.

However, they still needed to decide on a gas turbine technology, but eventually settled on a free turbine configuration that was more expensive, but had crucial advantages such as less starting power requirements, simplified controls for fuel and the ability for fixed-wing aircrafts to purchase off the shelf propellers rather than custom ones. Once the team decided to move in this direction, they still were not ready to get to work since they had to travel to Pratt & Whitney’s headquarters to convince the chief engineer that their plan was the right one. Upon securing his approval, the jubilant team started working on the ambitious project.

Unfortunately, their work was a blight on company balance sheets. The new design attempts led to a sort of development nightmare, but the chief engineer that approved the project still had faith in the vision. As a result, he sent a team of six experts spearheaded by a highly skilled engineer named Bruce Torell. The goal was to get the project back on track, and history reveals that this historic engine would have likely failed without his aid.

Progress was quickly made thanks to Torell’s engine expertise, but then the team faced obstacles from PWC itself. Despite aggressive attempts to terminate the project, work continued and was finally ready for flight testing in 1961. A search began for a suitable twin engine airplane to test with the PT6, and the team chose Beechcraft C-45 “Expeditor”. This Beechcraft Model 18 was equipped with two R-985s, meaning that the traditional radial engines played a huge role in the development and rise of the PT6. While further tweaks to the engine were made, the future of airplane engines was clear. Gas turbine technology was here to stay, it was just a matter of whether the PT6 was the engine that would dominate the airplane industry. It did, thanks to Beechcraft, the same company that used P&W’s radial R-985 engines of decades past. With that agreement, the PT6 finally saw mainstream success that produced its dominant run as one of the great engines of history and in fact was the first engine ever put on a King Air.

Growing global markets and ever-increasing customer bases have led to thousands of start ups, emerging growth companies, and the success of established companies. However, each company within this broad, three-tier classification can benefit from the use of a supply chain provider. As a company approaches the point of becoming an established company, the use of a supply chain provider becomes more prominent, and most established companies have an existing partnership with one of the major shipping providers. However, even some established companies continue to operate and handle all supply chain processes in-house, which represents an extreme risk for the company. If the in-house processes fail, the company tumbles and fails as well. Rather than waiting for your company to titter on the edge of complete failure, take a look at how supply chain services will improve your telecommunications abilities, networking needs, customer service departments, and storage of data within the cloud.

After all these years, the legacy King Air still has it! What's your favorite corporate/business #aviation #aircraft?

A photo posted by Covington Aircraft (@covingtonaircraft) on

Turbine Vs. Radial, Why the Comparison?

I’ve been privileged to know both the PT6A and the 9-cylinder Pratt engines. Both engines operate on a different technique for deriving horsepower from the combustion process, but at heart they are still both internal combustion engines that share the same engineering DNA.

radial blower sectionOne of the most complex parts of the R-1340/R-985 engine, which has remained relatively unchanged since December 24, 1925 when the very first R-1340 roared to life, is the supercharger or blower section. The blower section, which also serves as the anchor-point when installing the engine, is attached to the rear power case. The circular case receives the fuel/air mixture from the impeller assembly through diffuser channels then delivers the fuel/air mixture to the cylinders via the intake pipes. The blower is driven directly by the crankshaft through a spring loaded gear coupling located at the aft section of the crankshaft assembly. This ingenious design helps protect the blower gearing from sudden acceleration or deceleration. The spring loaded gear drives the floating gear. The impeller assembly, being indirectly driven by the crankshaft, turns ten or even twelve times crankshaft speed.

rise of the pt6a impellerIn like manner the PT6A Impeller is located in the gas generator housing which is the anchor point when installing the engine. The centrifugal impeller delivers air through diffuser tubes to the combustion chamber. The hot gases flow through a series of turbines which produce horsepower to the propeller shaft.

The impeller is only one area of similar design and function.  The reduction gearing in both the PT6A & R-1340G engines are remarkably similar as well as many other features. It is not rise of the pt6adifficult to see a common engineering theory. Many pilots and mechanics love the history and engineering that goes along with engines and aircraft. Certainly looking and comparing two of the legacy engines from Pratt & Whitney is enjoyable information for many in the aviation community. I have always found it entertaining that as the PT6A engine took its first breath of life, there were R-985 engines on each side! The photo (left) is of the first flight of the PT6A, being test flown on a Beech 18 (May 1961).

In closing, I am a mechanic that holds to the history of aviation. Learning about the past can certainly give insight to the present while possibly holding a glimpse into the future. Drawing a comparison between these two engines certainly does that.

– Rob Seeman, Covington Aircraft Operations Manager

 

Share and Enjoy

  • Facebook
  • Twitter
  • Delicious
  • LinkedIn
  • StumbleUpon
  • Add to favorites
  • Email
  • RSS