Sea King Pylon Repair and Overhaul by

Anick Chiasson

Intermediate Aero/Mechanical EngineerRotary Wing Engineering

IMP AEROSPACE

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IMP AEROSPACE

IMP Aerospace, P.O. Box 970, Enfield, Nova Scotia, Canada B2T 1L5Tel. 902. 873.2250 • Fax 902 873 2290 • e-mail. impad@impgroup.com

Website. www.impaerospaceanddefence.com

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• Introduction

• Overview of the Pylon

• Areas of Interest on the Pylon

• Engineering Process

• Area 1: Tail Gearbox (TGB) Support Fitting

• Area 2: Pylon Fold Fitting

• Area 3: Oversized Rivets on left side of a Pylon

• Area 4: Hinge fittings

• Area 5: Oversized Fasteners at Hinge Fittings

• Questions

Presentation Outline

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Introduction of IMP Group Ltd.

IMP Group Ltd.

IMP AEROSPACE & DEFENCE

IMP AEROSPACE Engineering Branch

Rotary Wing Engineering

Fixed Wing Engineering

Aeronautical Support

Engineering

Specialty Engineering

Technical Publications

Integrated Logistics Support (ILS)

= 22

= 30= 29

= 12= 26= 32

Number of professionals

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Overview of the Pylon

Pylon

The Pylon is the tail end of the aircraft.

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• The Pylon holds the Tail Rotor and the Stablilizer.

• The Intermediate Gearbox (IGB) and the Tail

Gearbox (TGB) are installed on the Pylon.

• The Pylon is under intense load (torsion and

bending).

• The Pylon is a critical primary component of the

Sea King.

Overview of the Pylon

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Areas of Interest on the Pylon

Area 1 Area 3

Area 5

Area 4

Area 2

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Engineering Process

• Sea King part or component is inducted in our facility.

• The damage is assessed.

• Production department requests Engineering services for a serviceability assessment.

• Engineering team calculates safe limits for rework/repair.

• Engineering team prepares a detailed repair scheme document.

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Area 1 : TGB Support Fitting

• Damage found inside barrel nut bore holes and bolt holes

• Damage found on Tail Gearbox (TGB) mounting pads

Barrel Nut Holes

Mounting Pads and Bolt Holes

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The power fold system was added to the Canadian version of the Sea King.

Area 2: Pylon Fold Fitting

Pylon Fold Fitting

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Area 3: Oversized Rivets on left side of a Pylon

Row of oversized Rivets (Quantity 55) was discovered at overhaul. The rivets found were 1/4” and the OEM design was 3/16”.

UPFWD Rivet #1

Rivet #55

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Area 4: Hinge Fittings

Upper Hinge Fitting(Top View)

•The lugs are two of the

attachment points to the

aircraft fuselage.

•The four mounting pads

are to install the

Intermediate Gear Box.

Lugs

IGB Mounting Pads

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Upper Hinge Fitting

FWDUP

Hi-Lok fasteners qty 11 on either side at upper hinge fitting

Hi-Lok fasteners qty 8 on either side at lower hinge fitting

Area 5: Oversized Fasteners at Hinge Fittings

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Initial Problems:

•11 pylons with oversized fasteners at installation of Upper and Lower Hinge Fittings.

•No approved documentations were found to substantiate the oversized fasteners.

•Up to 0.292” from their original design size of 0.188”.

•Biggest problem was the lack of acceptable edge distance (ED) on the different structure parts.

Area 5: Oversized Fasteners at Hinge Fittings

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Assessment:

Repairing the pylon by replacing the structure affected; and revert to 3/16” fasteners:

•400 man-hours per pylon

•Lead time to get parts

•Material cost

•Manufacturing hours to

manufacture parts needed

Option 1 Option 2

Analyzing the damage for serviceability:

•The margins of safety of the

Fittings were high

•The skin, cap angles and

doubler had to be analyzed

•The analyses would render at

least 8 pylons serviceable

Area 5: Oversized Fasteners at Hinge Fittings

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Example of the multiple layers within the Pylon.

Plugging the oversized holes was required for this repair.

Area 5: Oversized Fasteners at Hinge Fittings

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Results:

•Engineering was able to analyze the structure with

the oversized fasteners.

•Those completed and approved analyses rendered 6

pylons serviceable.

•More pylons will be deemed serviceable using the

completed analyses.

•Fatigue limits in terms of life span for each pylon were

achieved.

Area 5: Oversized Fasteners at Hinge Fittings

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Area 5: Oversized Fasteners at Hinge Fittings

Example of spliced skin (above)

Example of less than 2D edge distance (left)

Splice cut line

Edge Distance (ED) less than 2D

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Please come see a Pylon at our booth to discuss any further questions that you may have!

Questions

Thank you for the opportunity to highlight IMP’s Pylon R&O capabilities!