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Sea King Pylon Repair and Overhaul by
Anick Chiasson
Intermediate Aero/Mechanical EngineerRotary Wing Engineering
IMP AEROSPACE
1
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
2
• 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
3
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
5
• 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
7
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.
8
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
9
The power fold system was added to the Canadian version of the Sea King.
Area 2: Pylon Fold Fitting
Pylon Fold Fitting
10
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
11
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
12
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
13
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
14
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
15
Example of the multiple layers within the Pylon.
Plugging the oversized holes was required for this repair.
Area 5: Oversized Fasteners at Hinge Fittings
16
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
17
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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