How Jim Savage Gets the 1939 Spartan Executive So Shiny

This blog is republished with the permission of Jim Savage. His website, VintageSpartanAircraft.com which features his 1939 Spartan Executive, is a must visit.

What do you do to make your Spartan so shiny?  That’s a question I am often asked and the answer may be easier than you expect. Obviously, it takes quite a bit of polishing, using quality polishing supplies and good polishing techniques. Most experienced metal polishers with bare metal airplanes already know that.  The missing piece has to do with how light behaves when it reaches the airplane. Specifically, it is either reflected or it is absorbed.  The more light that is reflected, the shinier the airplane appears to be.  The trick is to eliminate anything that absorbs the light. In the case of Spartan NC17634, it has minimal paint trim, so there is more surface available to reflect light. Of course, that holds true for many bare metal airplanes.  The other source of light absorption is the tiny black rings around each of the rivet heads.  Although often unnoticed unless you are specifically looking for them, almost every bare metal has these light absorbing rings, including ones that have been judged as Grand Champions.  They originate during the normal polishing process and over time and many polishings, they slowly accumulate.  With the passage of time, these rings become extraordinarily difficult to eliminate.  

While a tiny black ring around a single rivet doesn’t seem like much, consider what the cumulative amount is if you have 9000+ polished rivets, as is the case with NC17634. To the best of my knowledge, there is no magic potion that easily removes the black residue.  It is simply a matter of finding a process that works best for you and then proceeding, one rivet at a time.  While the removal of all traces of black from every rivet of an entire airplane is a daunting task, the results are clearly noticeable.   

Here are some close-up pictures rivets on a 1939 Spartan Executive.  The first nine pictures show examples of what domed rivets with black rings look like on a highly polished airplane.

The next nine pictures show similar views of the same Spartan, after removal of the black rings.

For those of you who are really, really curious about how long it took to remove all traces of black from the 9000 rivets on the Spartan, it is probably far more than you can imagine and likely far more than you will believe. It took approximately 800 hours of effort but as the following picture shows, the final results can be stunning.

More Pictures of the Spartan 1939 Executive

The Feeling Of Flying Radials

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For private pilots and aircraft owners, the motivation behind this pursuit can be personal, but it can also be practical. Along with a love of aeronautics, pilots are also in tune with engine performance, as this does impact the overall experience. For owners of small commercial fleets, a focus on safety and efficient performance can often be the deciding factor in terms of what type of aircraft and what type of engine will provide the strongest asset.

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Australian company to restart production of the iconic Albatross flying boat with the improved G-111T Variant

Australian company Amphibian Aerospace Industries will build a new version of the legendary Albatross flying boat.

Australian company Amphibian Aerospace Industries (AAI) will build a new version of the legendary Albatross flying boat. Named G-111T, the “new Albatross” will feature new Pratt & Whitney PT6A-67F engines providing substantially improved performance, fuel economy and reliability.

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Textron Aviation’s Cessna SkyCourier gets flight-ready

WICHITA, Kan. (Feb. 4, 2022) – Textron Aviation today announced the rollout of the first production unit of the twin-engine, large-utility turboprop, the Cessna SkyCourier, at the company’s manufacturing facility in Wichita. The new, clean-sheet design has allowed for the incorporation of the latest state-of-the-art assembly and fabrication processes and techniques into the manufacturing of the aircraft.

The Cessna SkyCourier is designed and produced by Textron Aviation Inc., a Textron Inc. (NYSE:TXT) company.

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Pratt & Whitney unit gets deal for DART-750 engines

Pratt & Whitney Canada, a business unit of Pratt & Whitney, announced today that Diamond Aircraft has selected the PT6A-25C engine to power its new DART-750 aircraft, an all-carbon fibre tandem turboprop trainer equipped with state-of-the-art avionics.

“We are pleased that Diamond Aircraft has selected the PT6 turboprop, the most popular engine in its class, to pursue its DART program,” said Nicholas Kanellias, Vice President, General Aviation, Pratt & Whitney Canada. “The selection of the PT6A-25C for the Austrian-designed and manufactured DART-750 acrobatic trainer, further asserts the dependability, versatility and flexibility of this engine family.”

“The PT6A-25C is a proven engine that is already certified, allowing us to target 2023 for the basic EASA civil certification of the DART-750,” said Liqun (Frank) Zhang, Chief Executive Officer, Diamond Aircraft. “We see huge potential for the aircraft in the government training market and we believe the DART-750 is the perfect choice for the future basic training of pilots.”

Known for its broad power range, dependability and proven performance in all flying conditions and environments, the PT6A engine family is in a class of its own having flown more than 425 million hours, building upon the experience gained within the entire Pratt & Whitney Canada fleet at over 900 million flying hours. The PT6A has seen 120 enhancements made in the past 10 years alone, and more than 50,000 engines have been produced; 25,000 of them still fly. The PT6 turboprop is the benchmark in reliability and is considered to be the most versatile turboprop engine in General Aviation, which speaks to its dependable performance in single- and twin-engine aircraft.

“Diamond Aircraft has been a dynamic player in the General Aviation market for more than 40 years and we welcome the company as the latest airframe manufacturer to realize the tremendous capabilities of our PT6A engine,” said Anthony Rossi, Vice President, Business Development, Pratt & Whitney Canada. “We worked closely with Diamond Aircraft to determine the best powerplant for the DART-750 and believe the PT6A-25C will provide the exceptional pairing our customer is looking for.”

Hot Section Inspections

Maintenance time is just ahead for many operators. Shops are starting to fill out schedules for off-season work.  One of the maintenance items that is frequently discussed is the need for an engine hot section inspection.  While hot section inspection time requirements may differ by engine model, the “mid TBO” recommendation usually applies. Performance loss can also dictate the need for an inspection.  For example, the PT6A-34AG engine TBO (Time Between Overhauls) is 4000 hours, and hot sections are recommended at 2000 hours.  For the PT6A-65AG, the basic engine TBO is 3000 hours, and the recommended hot section inspection is 1500 hours.  All this information exists for all engine models in various Pratt & Whitney Canada service bulletins.  Time constraints are listed in service bulletins, but each engine model’s maintenance manual defines the hot section inspection criteria.

What exactly is a hot section inspection?  The hot section inspection is the way of making sure the condition of some of the hardest working parts in your engine can continue to do the job up to the next inspection interval or until TBO.  The PT6 engine is all about efficiency, and the hot section inspection is a simple and fast way to confirm the engine is not losing efficiency in this extreme environment.  Because of the temperature and forces applied to the parts in the hot section, a wide variety of factors can change efficiency just through normal operation.  Fretting, wear, cracking, and rubbing all have a chance to exist in the hot section, and all can negatively affect your engine’s performance.

When the engine is split to perform the hot section inspection, one of the first tasks is to measure the compressor turbine blade tip clearance.  Tip clearance is one of the key areas for efficiency.  On a PT6A-34AG, for example, the median tip clearance is .013”.  That is only the thickness of a couple of business cards.  That clearance is awfully close for a disk that spins thousands of revolutions per minute in temperatures of hundreds of degrees. When those tip clearances begin to increase, you lose performance. In the cockpit, that means the engine is not making power because of temperature limitations.

After tip clearances are measured, the turbine disk is removed, and the rest of the hot section parts are checked for deterioration, distress, or other problems.  Once repairs are made, and issues addressed, components are resurfaced and resealed as needed.  The compressor turbine blade tip clearance is reset to get maximum efficiency by changing and/or grinding the segments.  Then the hot section is reinstalled. That is a basic overview.

There are additional requirements as part of the inspection.  Bleed valve and compressor condition must be checked.  The gas generator case has inspection criteria.  The fuel nozzles, the power turbine stator and housing, exhaust duct, oil strainers, oil filters, and chip detectors are also checked.  No one wants to invest time and money into a hot section only to find out the compressor has issues and the engine must be removed.  What if you find out that the gearboxes are making metal?  Perhaps distress in your hot section is being caused by a fuel nozzle issue?  Proper inspection of all parts and fulfilling all inspection criteria are essential when it comes to hot section inspection.

I touched on some of the things that we are doing during your hot section inspection.  Just remember it is more than a split and peak at the parts.  We want to ensure the engine is safe for the operator and can be operated to its fullest when needed.  Preventative maintenance and inspections are also a way to keep costs down.  If problems can be detected early and repaired, it is less expensive than replacing parts like a vane ring or turbine blades.

As we head into maintenance season this year, review your engine times and be sure to discuss the need for a hot section inspection.  You want to make sure once you get through the downtime, the airplane and engine are primed and ready for another successful spray season.

Please reach out to me at robertc@covingtonaircraft.com if you have any questions, and I’ll be glad to assist.

This article first appeared at Aerial Fire Mag here.

The PT6A-50 Powered De Havilland Canada DASH-7

During the 1950s and 1960s, the aircraft manufacturer De Havilland Canada (DHC) acquired extensive experience in the construction of small and medium capacity transports with short takeoff & landing (STOL) capabilities, such as the “Otter”, “Twin Otter”, “Caribou”, and “Buffalo”. In the early 1970s, DHC decided to create a four-engine turboprop medium STOL airliner, which emerged as the “DHC-7” AKA “DASH-7”. The DASH-7 was only built in modest numbers, though it did prove useful as a military surveillance platform. DHC followed it with a twin-turboprop airliner, the “DHC-8” AKA “DASH-8”, which proved much more successful. This document provides a history and description of the DASH-7 and DASH-8.

DASH-7

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Radial Engine Preservation: 5 Simple Tips to Follow for Radial Engine Storage Pre-Service

“How long did you say the engine sat idle?”  What should be done to an engine to return it to service after it has sat idle for years? Answering that question requires the answer to several other questions: Was the engine preserved before it was put into storage? Was it stored in a climate controlled facility? No? Out in the weather? Were the exhaust stack(s) and carburetor air inlets plugged? Was the engine periodically run-up to operating temperature? Did it have preservative oil ran in the engine before entering storage?

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