Pazmany PL9-STORK

Pazmany Aircraft Corporation has been dedicated to the design of homebuilt aircrafts for over 30 years. Mr. Ladislao Pazmany, president of Pazmany Aircraft Corporation, designed several light airplanes for amateur construction. The PL-1, a two place all metal airplane, prototype was built by Mr. John Green and Keith Fowler and it was flown for the first time in March of 1962. The test pilots were CDR Paul Hayek, USN and Lieu. Richard Gordon, who is best known as one the Gemini astronaut.

Set of plans and instructions for building the PL-1 were sold to amateur constructors in USA, Canada, Australia, Norway, Taiwan, Argentina, etc. Shortly after flight trials of the PL-1 began, Mr. Pazmany initiated a complete redesign of the aircraft. The developed redesign was called PL-2.

The PL-2 is a reliable, safe, and well-engineered two-place airplane. The many units already built by amateurs and by military factories have accumulated more flying hours than any other “amateur built” aircraft design.

In the early l970's Mr. Pazmany started the design of a single-place airplane called PL-4. PL-4’s prototype was flown on July 9, 1972, and has it has been built by amateur builders around the world.
Mr. Pazmany latest design is the PL-9, a three-quarter-scale version of the Fieseler Storch. The original German Luftwaffe Fieseler F-156 Storch was an outstanding W.W.II airplane, designed to take off and land in extremely short distances.

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Fieseler Fi 156 Storch

The original German Luftwaffe Fieseler F-156 Storch was an outstanding W.W.II airplane, designed to take off and land in extremely short distances.
The Pazmany PL-9 Stork is backed up by more than 9000 hours of aeronautical engineering design in order to obtain the same flying and handling characteristics of the original German Aircraft.

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Pazmany PL-9 Stork Logo

The proven aircraft configuration has been designed for a number of functions such as: Border Patrol, Fish Spotting, Highway Patrol, Forrest Fire Detection, Property Surveillance, Farm Work, Pollution Detection, Missionary Work, Etc.

The Pazmany PL-9 design uses very popular materials between the amateur builders.The PL-9 fuselage is made of welded chrome alloy steel tube while aluminum sheet metal/fabric covered the wing and empennage.

The complete analysis of the Pazmany PL-9 main structure had been made completely by Mr. Pazmany, but recently the PL-9 fuselage has been modified to accommodate a rear door that allows an easy access to the passenger. Such modification could affect significantly the structural integrity of the fuselage.
Mr. Pazmany selected Optimum Solutions to verify such changes analyzing the PL-9 fuselage using Finite Element techniques.

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PL-9 Stork Fuselage model

A complete Finite Element Model of the aft portion of the PL-9 fuselage was created using detalied blueprints provided for Mr Pazmany. The analysis assumes that the fuselage is supported by Pin Joints and Roller Joints at the rear spar attach point as shown in the figure below.

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PL-9 Aft fuselage Finite Element Model

Three types of loads were analyzed, as defined by FAR 23
  • Symmetrical Horizontal Tail loads
  • Unsymmetrical Horizontal Tail loads
  • Vertical Tail Loads.
The worst Symmetrical load case imposed by the Horizontal Tail is the following:
  1. Maximum Down Load, Maneuvering, Maximum Down Control @ VA (FAR PART 23 Reference 23.423(a)(1)
  2. Maximum Up Load, Gust 50 FTS @ VC + Balance Load
The worst Unsymmetrical load case imposed by the Horizontal Tail according to FAR 23.427 is:
  1. Maximum Vertical Load on one side and 100-10(n-1)% on other side

The worst Vertical Tail load case is:
  1. Maneuver Load, Maximum Displacement @ 30 Degrees. (FAR PART 23 Reference 23.441(b)
  2. Gust Loads (FAR PART 23 Reference 23.443(d)
The loads selected were then applied at the end of the aft portion of the fuselage as shown in the figure above. A comprehensive stress analysis of the structure was completed and tension and compression loads were then calculated at each truss member. The smallest margin of safety (M.S.) of + 0.38 was found in one of the top member (compression) . This result seems to match Mr. Pazmany’s original hand calculations, therefore it can be concluded that the fuselage’s changes don’t affect considerably the overall structure integrity.

More information about Pazmany Aircraft Corporation can be found at