Modifications during service time

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LIST OF MODIFICATIONS - ENGLISH-BUILT DHC-1 CHIPMUNK SERIES


Mod No.

Date of Introduction

Applicability

Modification Title
H.23
23.03.49
T Mk10, Mk20,
21, 22, 22A

To Introduce ‘Z’ type Harness with Revised Anchorages

H.24
13.04.49
T Mk10, Mk20,
21, 22, 22A

To Introduce Fuel Filter in Fuel Feed Line to Engine

H.25


T Mk10, Mk20, 21, 22, 22A

To Improve Sealing Between Fuel Tank and Sump

H.26
07.09.49
T Mk10, Mk20,
21, 22, 22A

To Introduce Instruments with SAE Cases

H.27
04.10.49

T Mk10 Mk21

To Introduce Carbon Pile Type of Voltage Regulator in Lieu of Tyrell Type. Part A: Post Modification H.61. Part B: Pre-Modification H.61

H.28
07.10.49
T Mk10
Mk22, 22A

To Provide an Approved Protecting Coating in Battery Compartment. (not required when Mod. H.29

is embodied)

H.29
10.10.49

T Mk10 Mk20, 21

To Improve Venting of Battery Compartment and Make Holding Down Thumbscrews more Accessible

H.30
13.10.49
T Mk10

To Introduce Blanking Plates for use of S.A.E. Case Instruments in Existing Panels

H.31
13.10.49

T Mk10, Mk20, 21, 22, 22A

To Introduce ‘Lord’ Mountings in Series to Permit Increase Deflection of Instrument Panel

H.32
17.10.49


Miscellaneous Amendment

H.33
03.12.49


Miscellaneous Amendment

H.34
05.12.49
T Mk10, Mk20,
21, 22, 22A

To Introduce A.1134A (Interim Scheme Pending Modification H.36)

H.35
05.12.49
T Mk10

To Introduce Fixed Parts for TR.1936 VHF Radio on the 170th and Subsequent Aircraft

H.36
05.12.49

T Mk10 Mk22, 22A

Radio: To Introduce Removable Parts for TR.1936 10 Channel VHF Radio in Lieu of TR.1520 or TR.1920

H.37
05.12.49
T Mk10
Mk22, 22A

Radio: To Introduce Fixed Parts for TR.1934 or TR.1936 10 Channel VHF Radio

H.38
16.12.49

T Mk10 Mk20, 22, 22A

To Introduce SKF Bearing CBS/2 in Lieu of Torrington Bearing at Rudder Pivot Bracket

H.39
17.12.49
T Mk10
Mk22, 22A

To Introduce TR.1520 VHF 4 Channel Radio for ac without TR.1920

H.40
07.01.50
T Mk10, Mk21

To Reposition Hand Brake Lever Within Easier Reach of Pilot

H.41
09.01.50

T Mk10, Mk20, 21, 22, 22A

To Introduce Redesigned Fuel Cock Lever

H.42
09.01.50

T Mk10, Mk20, 21, 22, 22A

To Introduce Redesigned Control in cockpit for ‘Coffman’ Engine Starter

H.43
13.01.50
T Mk10, Mk20,
21, 22, 22A

To Delete Engine Data Plate in Cockpit

H.44
13.01.50
T Mk10, Mk20,
21, 22, 22A

To Introduce Fuel Tanks with Redesigned Attachment at Filler

H.45
20.01.50

T Mk10, Mk20, 21, 22, 22A

To Plug or Delete Canopy Plunger Hole at the 16.1 ins. Position from the Rail Front End

H.46
24.01.50
T Mk10
Mk21

To Redesign Canopy Release Mechanism to Prevent Wear of Canopy Release Cable and to Provide

Hole at Aft End of Canopy Rail

H.47
27.01.50
T Mk10, Mk20,
21, 22, 22A

To Introduce Standard A Locking of the Bolts Attaching the Tailplane Attachment Fitting to the

Bulkhead

H.48
09.02.50
T Mk10, Mk20,
21, 22, 22A

To Introduce Revised Labels which Alter the Max Speed at Which Flaps can be Lowered from 74 to

71 Knots

H.49
13.09.50

T Mk10, Mk20, 21, 22, 22A

To Introduce ‘Coffman’ Starter S7 Mk.2 Embodying Plessey Modification 90

H.50
20.02.50


Miscellaneous Amendment

H.51
24.02.50
T Mk10

Amendment to Chipmunk DIS

H.52
28.02.50
T Mk10, Mk20,
21, 22, 22A

To Introduce Modified Extension to Rear Engine Driven Fuel Pump Priming Lever (Post

Modification GM.1717)

H.53
28.02.50

T Mk10 Mk21, 22, 22A

To Simplify Design of Rear End of Exhaust Manifold

H.54
15.03.50
T Mk10, Mk20,
21, 22, 22A

To Introduce a Vent in Fuselage Side for Goggle (two stage colour) Demisting

H.55
15.03.50

T Mk10, Mk20, 21, 22, 22A

To Introduce more Robust Canopy Front Rollers (Superseded by Modification H.173)

H.56
16.03.50
T Mk10
Mk21, 22, 22A

To Add Auxiliary Vent Hole in Fuel Tank Stack Pipe Vent (Superseded by Modifications H.138 &

H.207)

H.57
16.03.50

T Mk10, Mk20, 21, 22, 22A

To Introduce Socket for Bowser Bonding Plug Adjacent to Fuel Filler Cap

H.58
30.03.50
T Mk10, Mk20,
21, 22, 22A

To Introduce Redesigned Sealing Glands at Throttle and Mixture Control Rods Through Firewall

H.59
25.03.50

T Mk10, Mk20, 21, 22, 22A

To Introduce Undercarriage Wheel AH.9389 with Improved Fixing for Brake Plate Location Blocks in Lieu of AH.9126

H.60
26.04.50
T Mk10

To Introduce Revised Protective Treatment and Finish on Ground Equipment

H.61
26.04.50
T Mk10, Mk20,
21, 22, 22A

To Revise Voltage Regulator Circuit to Avoid Burning Out Generator (Superseded by Modification

H.27)

H.62
26.04.50
T Mk10

To Introduce Strengthened Attachment Feet for Oil Tank Air Inlet Duct

H.63
26.04.50

T Mk10, Mk20, 21, 22, 22A

To Introduce Rivets to Reinforce Existing Spot Welds on Both Cockpit Seats

H.64
26.04.50
T Mk10, Mk20,
21, 22, 22A

To Improve the Fixing of Aileron Mass Balances

H.65
11.07.50
T Mk10, Mk20,
21, 22, 22A

To Introduce Support Strut for Plessey Cartridge Starter

H.66
24.05.50
T Mk10, Mk20,
21, 22, 22A

To Stiffen Tailplane Attachment Fittings to Prevent Panting of Front Spar Web

H.67
25.05.50

T Mk10, Mk20, 21, 22, 22A

To Introduce Larger Diameter Pulleys for Rudder Cables in Centre Fuselage

H.68
02.06.50


Miscellaneous Amendment

H.69
13.06.50
T Mk10, Mk20,
21, 22, 22A

To Lock Positively the Aileron and Rudder Stop Bolts

H.70
14.06.50

T Mk10, Mk20, 21, 22, 22A

To Introduce Improved Tailplane Attachment Fittings on Rear Fuselage Bulkhead

H.71
22.06.50
T Mk10, Mk20,
21, 22, 22A

To Provide a Means of Ensuring that the Canopy Emergency Panel Release Handle is in the “Safe”

Position

H.72
26.06.50

T Mk10, Mk20, 21

To Reinforce Oil Tank Mounting Feet (Interim Scheme Pending Modification H.81)

H.73
30.06.50
T Mk10, Mk20,
21, 22, 22A

To Improve the run of the Flexible Drive for Tachometer Generator and Introduce Redesigned

Fairlead

H.74
12.07.50

T Mk10, Mk20, 21, 22, 22A

To Introduce Redesigned Spinner A.66870 for Propeller in Lieu of A.66709 (Superseded by Modification H.190)

H.75
14.07.50

T Mk10,

Mk20, 21

To Introduce an Improved Tapered Actuating Rod in Brake Actuator in Lieu of Shouldered Type

H.76
19.07.50

T Mk10, Mk20, 21

To Strengthen Nose Cowl Lugs

H.77
25.07.50
T Mk10, Mk20,
21, 22, 22A

To Introduce Larger Diameter Pulleys on Rudder Control System in Front and Rear Fuselage and

Reduce Circuit Tension

H.78
03.08.50
T Mk10, Mk20,
21, 22, 22A

To Alter Shape of Slots for Clips in Undercarriage Leg Fairing (Superseded by Modification H.130)

H.79
03.08.50
T Mk10, Mk20,
21, 22, 22A

To Improve Method of Welding on Tailwheel Fork

H.80
03.08.50

T Mk10, Mk20, 21, 22, 22A

To Introduce a Test Point in Vacuum System at Rear of Instrument Panel

H.81
03.08.50

T Mk10, Mk20, 21, 22, 22A

To Introduce Redesigned Oil Tank with Improved Method of Attachment and Larger Diameter Filler Neck

H.82
14.08.50
T Mk10, Mk20,
21, 22, 22A

To Introduce Redesigned Support Bracket for Engine Speed Generator Mounting.

Part A: Mod. to Existing Bracket for Retrofit. Part B: New Bracket for Production and Replacement

H.83
17.08.50

T Mk10, Mk20, 21, 22, 22A

To Delete Attachment for Oil Cooler Inlet Duct at Firewall

H.84
17.08.50
T Mk10, Mk20,
21, 22, 22A

To Introduce Redesigned Mounting for Socket for Ground Electrical Services

H.85
15.09.50
Mk20, 21

To Introduce Electric Starter in Lieu of Coffman

H.86
20.09.50

T Mk10, Mk20, 21, 22, 22A

To Separate the Oil Drain form the Induction Manifold and to Improve the Induction Manifold Drain Pipe

H.87
29.09.50
T Mk10, Mk20,
21, 22, 22A

To Strengthen Flanges of Drain Outlet Assembly at Firewall

H.88
26.09.50
Mk21, 22A

To Introduce 12 Gallon Fuel Tanks

H.89
26.09.50

T Mk10, Mk20, 21, 22, 22A

To Introduce Fireproof Fairlead for Cables at Firewall

H.90
26.09.50
T Mk10, Mk20,
21, 22, 22A

To Introduce Steel Fairlead for Oil Pressure Capillaries at Firewall

H.91
27.09.50
Mk21

To Introduce Vacuum Gauges in Both Cockpits

H.92
09.10.50

T Mk10, Mk20, 21, 22, 22A

To Ensure Correct Adjustment of Undercarriage Torque Links Centre Hinge Joints and to Increase Diameter of Split Pin on Nut

H.93
09.10.50
T Mk10,
Mk20, 21, 22

To Introduce Redesigned Ratchet and Pawl for Brake Lever with Improved Hardening on Contact

Faces

H.94
30.10.50

T Mk10 Mk21

To Introduce Vent Hole in Fuel Contents Gauge. CANCELLED

H.95
30.10.50
T Mk10, Mk20,
21, 22, 22A

To Introduce Longer Oil Tank Vent Hose

H.96
01.11.50

T Mk10, Mk20, 21, 22, 22A

To Introduce a Strengthened Outer Elevator Hinge Bracket and Longer Attachment Bolts

H.97
09.11.50
T Mk10, Mk20,
21, 22, 22A

To Introduce a Stop in the Control Box for Wheel Brake Actuating Lever

H.98
14.11.50

T Mk10, Mk20, 21, 22, 22A

To Introduce Oil Cooler Blanking Plate

H.99
15.11.50

T Mk10

Mk20, 21

To Strengthen Top Nose Cowl Attachment

H.100
18.12.50

T Mk10, Mk20, 21, 22, 22A

To Introduce Strengthened Two-Stage Flying Practice Screens. Part A: Fixed Fittings. Part B: Amber Screens

H.101
28.12.50
Mk21, 22, 22A

To Introduce Bonding on Airframe Control Surfaces

H.102
01.01.51


Not Allocated

H.103
11.01.51


Miscellaneous Amendment

H.104
22.01.51
T Mk10, Mk20,
21, 22, 22A

To Introduce Extended Chord Rudder

H.105
23.01.51

T Mk10, Mk20, 21, 22, 22A

To Introduce Pren Type Cables for Aircraft Electrical Services

H.106
02.02.51
T Mk10, Mk20,
21, 22, 22A

To Reinforce Flange and Edge of Oil Cooler Air Scoop

H.107
14.02.51

T Mk10, Mk20, 21, 22, 22A

To Introduce Watch Holder Stores Ref: 6A/1465 in Front & Rear Cockpits

H.108
01.03.51
T Mk10, Mk20,
21, 22, 22A

To Improve the Hot and Cold Carburettor Air Intake Control

H.109
05.03.51

T Mk10, Mk20, 21, 22, 22A

To Introduce Wiring to Provide Electrical Heating for the Pitot Head (Post-modification H.27)

H.110
21.03.51
T Mk10

To Introduce Two-Stage Blue Flying Practice Screens

H.111
19.04.51

T Mk10, Mk22, 22A

To Introduce TR.1934 Aerial Type 228 in Lieu of TR.1936 and Aerial Type 226 (Superseding Modification H.36)

H.112
04.05.51
Mk20 only

To Introduce Plessey PTR61 Mk.2 VHF Radio with Dual Control

H.113
04.05.51

T Mk10, Mk20, 21, 22, 22A

To Correct External Fuel Markings Adjacent to Filler Cap

H.114
22.05.51
T Mk10

Part A: To Introduce 1 Gallon Drinking Water Tank with Fixed Stowage. Part B: To Introduce Stowage for Signalling Strips

H.115
22.05.51

Mk21 Only 2 ac for King’s

Cup Air Race

To Introduce Long Range Fuel Tank

H.116
28.05.51
T Mk10, Mk20,
21, 22, 22A

To Introduce an Additional Ratchet Plate to “Double up” the Bearing Surface for Pawl on Flap Lever

H.117
28.05.51
T Mk10, Mk20,
21, 22, 22A

To Introduce a Strengthened Bolt Plate for Engine Mounting at Stabilising Struts

H.118
02.06.51

T Mk10, Mk20, 21, 22, 22A

To Introduce a Hole in Nose Cowl for Rocker Box Cooling

H.119
19.07.51
T Mk10, Mk20,
21, 22, 22A

To Introduce Heavier Gauge Rear Tubular Member on Canopy Frame

H.120
25.02.52

T Mk10, Mk20, 21, 22, 22A

To Introduce Strengthened Pulley Mounting Bracket in Fuselage for Flap Controls

H.121
15.06.51
T Mk10, Mk20,
21, 22, 22A

To Replace Light Alloy Bracket by Steel for Strut Attachment at Tailplane Rear Spar

H.122
16.06.51

T Mk10, Mk20, 21, 22, 22A

To Decrease the Pitch of Rivets for Stringers in Top Skin of Main Plane in Area Directly Outboard of Tank Bay

H.123
19.06.51
T Mk10, Mk20,
21, 22, 22A

To Introduce Redesigned Rear Roller Attachment Bolt and Washer for Canopy (Partly Superseded by

Modification H.182)

H.124
27.06.51

T Mk10, Mk20, 21, 22, 22A

To Delete Spring-loaded Non-return Valve Part. No.s SPE170 from Fuel System Replace by SPE1183 (Non-Spring-Loaded Type) (Superseded by Modification H.165)

H.125
28.06.51

T Mk10, Mk20, 21, 22, 22A

To Strengthen the Attachment of Rudder Fairings and Tail Cone

H.126
30.06.51
T Mk10, Mk20,
21, 22, 22A

To Reposition Fuel System Non Return Valves to Improve Accessibility

H.127
30.06.51
T Mk10, Mk20,
21

To Introduce ‘Investment’ Cast Flange for Exhaust Manifold

H.128
11.07.51

T Mk10, Mk20, 21, 22, 22A

To Prevent Fixing Bolt Rotating in Torque Link Lugs on Undercarriage

H.129
11.07.51
T Mk10, Mk20,
21, 22, 22A

To Introduce Stiffened Rudder Pedal

H.130
11.07.51

T Mk10, Mk20, 21, 22, 22A

To Introduce a Redesigned Undercarriage Compression Leg Fairing

H.131
11.07.51
T Mk10, Mk20,
21, 22, 22A

To Reposition Ground/Flight Switch

H.132
23.07.51

T Mk10, Mk20, 21, 22, 22A

To Redesign Attachment of Knurled Nuts at Top of Dashboard

H.133
27.07.51
T Mk10, Mk20,
21, 22, 22A

To Reinforce Canopy Rear Tubular Member (for Retrospective Application Pending Introduction of

New Canopies to Modification H.119)

H.134
03.08.51

T Mk10, Mk20, 21, 22, 22A

To Introduce Redesigned Shock Absorber for Tailwheel

H.135
03.08.51
T Mk10, Mk20,
21, 22, 22A

To Introduce Improved Method of Adjustment for Friction Device in Tailwheel.

Part A: Using Existing Spindle. Part B: Using Longer Spindle

H.136
20.08.51

T Mk10, Mk20, 21, 22, 22A

To Provide a Strengthened Tailwheel Yoke & Provide Increased Clearance at Tail Cone

H.137
29.08.51
Mk21, 22, 22A

To Reduce the Maximum Quoted Diving Speed from 173 to 155 knots

H.138
03.10.51
T Mk10, Mk20,
21, 22, 22A

To Introduce Improved Type of Fuel Tank Vent (Superseded by Modification H.207)

H.139
03.10.51

T Mk10, Mk20, 21, 22, 22A

To Introduce a Stiffener at Fuel Filter Mounting on Firewall (Superseded by Modification H.181)

H.140
03.10.51
T Mk10

To Introduce Switch Type 896 (with spring loaded toggle) in Lieu of Switch Type 170 in “Press to

Mute” Circuit in VHF Rear Control Box. CANCELLED

H.141
03.10.51

T Mk10, Mk20, 21, 22, 22A

To Obtain more Clearance for Rudder Bar Throughout its Movement to Avoid Rudder Jamming

H.142
09.10.51
T Mk10, Mk20,
21, 22, 22A

To Reposition Oil Pressure Gauge Capillaries from Engine to Bulkhead

H.143
12.10.51
Mk21, 22, 22A

To Introduce Plessey Fireproof Cover for Cartridge Starter

H.144
17.10.51
Mk20 only

To Introduce Suppressor Type Y1 in Lieu of Type H No.2

H.145
18.10.51
T Mk10

To Introduce Protective Covers for Wheels

H.146
25.10.51
T Mk10, Mk20, 21, 22,
22A

To Improve Attachment of Lower Engine Support Fittings to Fuselage. Part A: Retrofit. Part B: Present Production using Countersunk Parts. Part C: Future Production using New Parts.

H.147
31.10.51

T Mk10, Mk20, 21, 22, 22A

To Introduce 1.0” Wide Lassovic PVC Adhesive Tape to Fuselage in the Vicinity of Wing and Empennage Fairings

H.148
12.11.51
T Mk10, Mk20,
21, 22, 22A

To Introduce Wire Mesh Screen and Retaining Unions in Suction Line of Vacuum System

H.149
18.11.51

T Mk10, Mk20, 21, 22, 22A

To Introduce Redesigned Elevator Central Hinge Fitting with Bosses and Centre Bolt in Lieu of Pin. Part A: Retrofit. Part B: Production

H.150
28.11.51
T Mk10, Mk20,
21, 22, 22A

To Prevent Draught Entering Rear Cockpit

H.151
06.12.51

T Mk10, Mk20, 21, 22, 22A

To Introduce Improved Assembly of Flap Operating Link

H.152
27.12.51
Mk21

To Introduce Marker Beacon BC.1033 and Range Receiver BC.453

H.153
28.12.51
T Mk10, Mk20,
21, 22, 22A

To Introduce Downward Identification Lamp Type ‘D’ (Amber) on Port Side of Aircraft and Delete

Existing Lamp from Starboard Side

H.154
01.01.52
Mk20, 21

To Introduce Fixed Parts for STR 9x 10 Channel VHF Radio

H.155
01.01.52
Mk20, 21

To Introduce Removable Parts for STR 9x 10 Channel VHF Radio

H.156
09.01.52

T Mk10, Mk20, 21, 22, 22A

To Introduce Mounting Assembly Type 873/2 and Improve Clearances around VHF Radio (when 10 Channel VHF is fitted)

H.157
09.01.52
T Mk10, Mk20,
21, 22, 22A

To Continue the Existing Slot in the Canopy Rail though the Rear Fairing

H.158
16.01.52

T Mk10, Mk20, 21, 22, 22A

To Introduce Suction Connection Type D Stores in Lieu of Type A for the Turn and Slip Indicator

H.159


T Mk10, Mk20,
21, 22, 22A

To Insulate Soldered Tags for Bulb Holder in VHF Control Box

H.160
22.01.52

Mk21, 22, 22A

Additional Night Flying Equipment to Meet ARB Requirements

H.161
23.01.52
T Mk10, Mk20,
21, 22, 22A

To Introduce Air Speed Indicator Smiths Type 167.AS Calibrated 30 - 210 Knots in Lieu of Type

159.AS 20 – 210 Knots

H.162
23.01.52

Mk20, 21, 22, 22A

Part A: To Introduce Patch Plates for Cut-Outs on Spinner. Part B: To Introduce Clearance Holes to Spinner Nose and Adhesive Tape to Base

H.163
04.02.52
T Mk10, Mk20,
21, 22, 22A

To Introduce Redesigned Bracket for Rudder Bar with Improved Ball Race Housing

H.164
03.04.52
Mk21, 22A

To Introduce Smiths Fuel Gauge 1632 FG Fitted with Luminous Dial FG 5024

H.165
03.04.52

T Mk10, Mk20, 21

To Introduce Non-return Valve Type SPE N375 Mk 1 in Lieu of Type SPE 1183 (Superseded by Modification H.199)

H.166
23.04.52

T Mk10,

Mk20, 21

To Reinstate Switch Type 170 in Press-to-Mute Circuit

H.167
15.05.52
T Mk10, Mk20,
21, 22, 22A

To Introduce a Stronger Internal Reinforcing Bracket and Internal Gusset Plate on Tailplane at Shock

Absorber Strut Attachment

H.168
29.05.52
T Mk10, Mk20,
21, 22, 22A

To Introduce Hoffman Self-Aligning Bearing N.1156 in Lieu of SKF 13303 in Elevator Connecting

Rod (under rear seat)

H.169
29.05.52

T Mk10, Mk20, 21, 22, 22A

To Ensure Correct Adjustment of Brake Levers

H.170
06.06.52
T Mk10, Mk20,
21, 22, 22A

To Improve the Attachment of Aileron Sprocket to Vertical Pivot Tube

H.171
10.07.52

T Mk10, Mk20, 21, 22, 22A

To Substitute Shackle Pin in Lieu of Bolt at Front Pilots Shoulder Strap Attachment

H.172
10.07.52
T Mk10, Mk20,
21, 22, 22A

To Obviate Chafing Between Canopy Leading Edge and Windscreen Mask

H.173
10.07.52

T Mk10, Mk20, 21, 22, 22A

To Change Front Canopy Rollers to Sliding Blocks

H.174
10.07.52
Mk20, 21

To Introduce Range Receiver BC.453

H.175
16.07.52


Miscellaneous Amendment

H.176
01.08.52

T Mk10,

Mk20, 21

To Introduce a Spring Over-riding Device in Brake Control Circuit. CANCELLED

H.177
01.09.52

T Mk10, Mk20, 21, 22, 22A

To Provide Close Tolerance Bolt in Lieu of Standard at Front Wing to Fuselage Joint

H.178
05.09.52
T Mk10, Mk20,
21, 22, 22A

To Introduce Reinforcing for Fin Post (when Mod H.104 is Embodied) (53 ac only)

H.179
12.11.52

T Mk10, Mk22, 22A

To Introduce Transfer for External and Internal Markings

H.180
27.11.52

T Mk10,

Mk20, 21

To Introduce Improvements in Brake Circuit to Actuators

H.181
30.12.52

T Mk10, Mk20, 21, 22, 22A

To Introduce Improved Method of Mounting Fuel Filter

H.182
30.12.52
T Mk10, Mk20,
21, 22, 22A

To Introduce a Square Slide in Lieu of Roller at Rear of Canopy

H.183
30.12.52
T Mk10, Mk20,
21, 22, 22A

To Provide Additional Treatment and Drainage Holes for Flap Inner Hinge Brackets

H.184
08.01.53

T Mk10, Mk22, 22A

To Introduce Turn & Slip Indicator Ref: 6A/3371 in Lieu of 6A/2676

H.185
28.01.53
T Mk10, Mk20,
21, 22, 22A

To Introduce an Improved Distance piece at Aileron Outer Hinge

H.186
20.02.53

T Mk10, Mk20, 21, 22, 22A

To Introduce Nose Cowl Reinforcing

H.187
25.03.53
T Mk10, Mk20,
21, 22, 22A

To Introduce Reinforcing on RH Corner of Cowling Undershield

H.188
25.03.53

T Mk10, Mk20, 21, 22, 22A

To Introduce Fuel Feed Pipe in Tungum in Lieu of Aluminium Between Cock & Fuel Filter

H.189
13.05.53
T Mk10, Mk20,
21, 22, 22A

To Introduce Compass Deviation Card Holder Mk 4 in Lieu of Mk 3

H.190
14.05.53

T Mk10, Mk20, 21

To Introduce Spinner A.66912 Mk 5 in Lieu of A.66870 Mk 4

H.191
16.05.53
T Mk10, Mk20,
21, 22, 22A

To Introduce a Loading Label in Luggage Locker

H.192
15.09.53

T Mk10, Mk20, 21, 22, 22A

To Introduce Guard over Muting Switch on Radio Control Box in Rear Cockpit

H.193
10.06.53

T Mk10, Mk20, 21, 22, 22A

To Introduce Improvements in Carburettor Heater System

H.194
10.06.53
T Mk10, Mk20,
21, 22, 22A

To Introduce Shorter Distance tubes for Front Engine Mounting Shear Rubber Assemblies

H.195
1.06.53
T Mk10, Mk20,
21, 22, 22A

To Introduce Modified Engine Mounting with Improved Bearing Face for Front Shear Rubber

H.196
13.10.53
Mk20, 21

To Introduce Plessey PTR 61F 6-Channel VHF Radio with Associated Controls and Wiring (replaces Mod. Chipmunk H.112)

H.197
04.12.53
T Mk10
All Civil Series

Gliding Towing Gear – To Introduce Glider Towing Facilities (See also H.121 & H.167)

H.198
07.12.53

T Mk10, Mk20, 21, 22, 22A

Mainplane: To Improve Fixing of Fabric to Wing

H.199
05.01.54
T Mk10, Mk20,
21, 22, 22A

Fuel System: To Introduce Improved Non-return Valve SPE 1957 in Lieu of SPE 1747

H.200
08.01.54

T Mk10, Mk20, 21, 22, 22A

Oil System: To Introduce Improved Washer for Oil Tank Filler Cap

H.201
13.01.54

T Mk10,

Mk20, 21

External Marking: To Introduce 82 Avgas Fuel and Markings (supersedes H.113) CANCELLED

H.202
08.02.54
Mk20

To Introduce Modified Instrument Panels for Uruguayan Air Force

H.203
08.02.54
Mk21

To Introduce Labels in Spanish for the Uruguayan Air Force. CANCELLED

H.204
08.0654

T Mk10, Mk20, 21

Electrical: To Introduce Two Unipren 6 Cables in Lieu of Dupren 6 Cable. CANCELLED

H.205
10.06.54
Mk21

To Permit the use of 9 Gallon Fuel Tanks in Lieu of 12 Gallon on Conversion from T Mk10 to Mk21.

CANCELLED 10.09.54

H.206
10.06.54

T Mk10, Mk20, 21, 22, 22A

Engine Controls: To Introduce Redesigned Throttle Rods

H.207
10.06.54
T Mk10, Mk20,
21, 22, 22A

Fuel System: To Introduce Balance Type Vents (supersedes H.138)

H.208
26.11.54

T Mk10, Mk22, 22A

Electrical: To Introduce Sea Grey Plastic Caps on Single Pole Switches in Cockpit

H.209
30.11.54
Mk20, 21

Radio: To Introduce Flexibly Mounted Aerial

H.210
12.04.55

Mk20, 21

22, 22A

Fuel Vent: To Introduce a Deflector on Rear Fuselage Underside to Prevent Fuel Entering Cockpit through Access Door

H.211
19.09.55

Mk20, 21

22, 22A

Electrical: To Introduce Suppressor Type Y1 in Lieu of Type H No. 2

H.212
25.11.55

T Mk10, Mk20, 21, 22, 22A

Fuel Vent: To Seal the Vent Fairing to Pre-vent possible Entry of Fuel Draining from Vent Pipes into Fuselage After Flying Inverted

H.213
28.02.56
Mk21

Fuselage: To Introduce Engine Data and No Smoking Labels, Name Plate and Weight Schedule

H.214
01.03.56
Mk21

Cockpit: To Prevent Brake Lever from Fouling Pilots Leg (Incorporating DOI 14484)

H.215
05.03.56
Mk21, 22

Braking System: To Introduce Header Tank and Pipe Line. Cancelled by H.245

H.216
05.03.56
Mk21

Engine Installation: To Prevent the Possibility of Gaps Between Firewall and Fuselage

H.217
05.03.56

T Mk10, Mk20, 21, 22, 22A

Fuel System: To Introduce Socket for Latest Bowser Bonding Plugs

H.218
06.03.56
T Mk10, Mk20,
21, 22, 22A

Elevator: To Introduce Strengthened Nose Ribs at Outer Hinge

H.219
10.04.56
Mk 22, 22A

Vacuum System: To Introduce a Vacuum Gauge on Front Cockpit Dashboard

H.220
13.09.56
Mk 22

Fuel System: To Modify Fuel Gauge with New Dial and Luminous Markings for Night Flying

H.221
24.04.56
T Mk10, Mk20,
21, 22, 22A

Cartridge Starter: To Introduce Type ‘SA’ Breech in Lieu of Type ‘S’

H.222
22.06.56

T Mk10, Mk20, 21, 22, 22A

Ground Equipment: To Introduce Modified Incidence Board for Tailplane

H.223
02.07.56
T Mk10, Mk20,
21, 22, 22A

Rear Fuselage: To Introduce Improved Attachment to Tailwheel Yoke

H.224
24.07.56

Mk21, 22, 22A

Cartridge Starter: To Introduce ‘SA’ Breech and Flameproof Cover in Lieu of ‘S’ Breech and Flameproof Cover CK3896

H.225
26.06.57
T Mk10, Mk20,
21, 22, 22A

Tail Unit: To Introduce Strengthened Extension Piece Rudder Torque Tube

H.226
20.02.57
T Mk10

Radio: To Introduce Mic-Tel Connector Type 10318 to TR.1920 and TR.1520 Radio Installation. CANCELLED

H.227
21.02.57
T Mk10

Electrical: To Introduce Flashing Navigation Lights. CANCELLED

H.228
16.08.57
Mk21, 22, 22A

Electrical: To Improve Bonding of Rudder to Fuselage

H.229
25.09.57

All Series

& T Mk10

Wing Root Rib: Improvement at Flap Operating Pulley Housing Mounting

H.230
02.09.57
All Series

Tailplane Rear Spar: To Increase Chamfers on Elevator Hinge Brackets

H.231
26.08.58
T Mk10, Mk20,
21, 22, 22A

To Introduce Anti-spin Strakes to Rear Fuselage

H.232


All Series

Engine Controls: To Introduce Re-designed Spring for Throttle and Altitude Control Rod End (pre and post modification H.206). Not used. See Modification H.236

H.233
07.03.56
T Mk10, Mk20,
21, 22, 22A

Fuel Tanks: Improved Water Drainage

H.234
24.03.58

All Series Except T Mk10

To Introduce Shouldered Bolt at Pivot Points on Rudder Bars for Inter-Connecting Rod

H.235
05.05.58
T Mk10,
Mk20, 21, 22A

To Provide Artificial Horizon 6A/1498, 6A/3290 or 6A/3827 as Alternatives to 6A/1519

H.236
23.06.58
All Series

Engine Controls: To Delete Alternative Ball Joint, Spring and Cup on Engine Throttle Control Rod

H.237
12.06.58

T Mk10, Mk22, 22A

Fuel System: To Mark Direction of Flow on All Pipe Lines and on Components where Incorrect Assembly of Components is Possible

H.238
09.02.59
Mk 23

To Introduce Agricultural Chipmunk Mk 23

H.239
09.02.59
Mk 23

To Introduce Spray Gear for Chipmunk Mk 23

H.240
16.12.58

All Series Except T Mk10

To Introduce Check Cable at Position of Flap Control Return Spring

H.241
13.11.58
T Mk10, Mk20
21, 22, 22A

To Introduce Additional Stiffening at Forward Fuselage Side Panels

H.242
20.11.58

All Civil Series & T Mk10

To Introduce Revised Battery Drain Pipes

H.243
12.06.59
Mk 23

Introduction of Modified Crop Spraying Gear (G-APOS only)

H.244
20.01.59
All Series &
T Mk10

To Introduce Shorter Snubber For Rear Engine Mounting Shear Rubber Assemblies

H.245
01.06.59
Mk21, 22, 22A
with H.215

Brake System: To Reposition Header Tank and Piping Forward of Firewall (Cancels H.215)

H.246
07.09.59
T Mk10, Mk20
21, 22, 22A

Engine Installation: To Introduce Slow Running Cut-out

H.247
27.08.59
All Civil Series

To Introduce Revised Position of Propeller Relative to Crank Webs

H.248


All Series T Mk10

To Revise Attachment Bolt at Flap Hinge Fitting at STN 60

H.249


T Mk10

Mainplanes: Introduction of Steel Wing Root Fittings. CANCELLED

H.250
04.05.60
T Mk10, Mk20,
21, 22, 22A

Electrical: To Introduce Re-routed Wiring to Pitot Head Heater in Port Mainplane

H.251
06.06.60

T Mk10, Mk20, 21, 22, 22A, 23

Elevator Rear Layshaft: Introduction of Improved Stops

H.252
10.05.61
All Civil Series
T Mk10

Firewall: To Introduce Packings Under Oil Tank Supports

H.253


WP903 Only

Fuselage: To Introduce Bristol Canopy with Bristol Flap Modification. CANCELLED

H.254
19.12.61
T Mk10
All Civil Series

Engine Cowling: To Introduce Glass Fibre Lower Nose Cowl Section Part No. FRDA 52473 in Lieu

of Metal Lower Nose Cowl Section Part No. C1-EC 79A/2

H.255
15.12.61

Civil Series T Mk10

Elevator Rear Layshaft: To Introduce Strengthen Bracket Part No. C1-CF 563A/2 in Lieu and By Conversion of C1-CF 563A/1

H.256
01.62
T Mk10

Miscellaneous: To Introduce Revised Fire Extinguisher. Cancelled and Replaced by Modifications

H.258 & H.259

H.257
15.01.62
T Mk10

Wireless Equipment: To Introduce Lightweight UHF TR ARI 18197/1. Cancelled and Replaced by Modification H.263

H.258
06.05.63
T Mk10
All Other Series

To Delete Stowage for Two-Stage Amber Screens

H.259
06.05.63
T Mk10
All Other Series

To Make Provision for and Introduce Fire Extinguisher 27N/299 in Lieu of 27N/12 and Bracket 27N/149 in Lieu of 27N/13 (Supersedes H.256)

H.260
10.06.63
All Civil Series
& T Mk10

Undercarriage: To Introduce Mainwheel Part No. AH.51981 in Lieu of AH.9389

H.261
03.01.64

All Civil Series & T Mk10

Controls: To Introduce Latch Plate Part No. C1-CF 1489 in Lieu of Latch Plate PC. No. C1-CF 1133A for Flap Control Lever (Superseded by H.272 then H.273)

H.262
19.02.64
All Civil Series
& T Mk10

Engine Mounting: To Introduce Larger Vent and Drain Holes in Tubular Structure. Part A: New

Spares. Part B: Retrospective Action

H.263
26.10.65
T Mk10

Wireless Equipment: To Introduce PTR170 Radio in Lieu of Existing VHF

H.264
25.06.64

All Civil Series & T Mk10

Controls: To Introduce Eye-end Adjuster Screw C1-CF 1491 and Turnbuckle C1-CF 1493 in Lieu of Eye-end Adjuster Screw C1-CF 1169 and Turnbuckle AS.2906 on Wheelbrake Control Cable

H.265
18.03.66
T Mk10
Civil Series

Instrument Installation: To Introduce and Make Provision for Mk.14 Fatigue Meter 6A/6487 and Air

Speed Switch

H.266
15.03.66
Mk20, 21, 22,
22A, 23

Fire Extinguisher: To Introduce a Guard Plate Over the Quick Release Mechanism of Fire

Extinguisher Mounting Bracket Type 27B (Graviner)

H.267
20.04.66

All Series & T Mk10

Alighting Gear: To Introduce Tailwheel Shock Strut Part No. C1-UT-189A in Lieu of C1-UT-131A.

H.268
31.08.66
All Civil Series
& T Mk10

Fuselage: To Introduce HTS Gusset Plates in Lieu of Aluminium Alloy Gussets at the Top Centre

Structure of Front Fuselage

H.269
31.08.66
All Series

Aerofoils: To Introduce HTS Pins in Lieu of Aluminium Alloy Rivets for Securing the LH & RH Elevator Interconnecting Flanges to Torque Tubes

H.270
04.11.66
All Civil Series
& T Mk10

Alighting Gear: To Introduce Special Bolt Part No. C1-UT-197 in Lieu of C1-20-UT9 on Tailwheel

Yoke Assembly

H.271
22.09.66
T Mk10

Miscellaneous: To Introduce Special Fluorescent Paint Scheme for Royal Navy Chipmunk T Mk.10 Aircraft

H.272
16.12.66
Civil Series

Controls: To Introduce Revised Latch Plate and Quadrant. Modification CANCELLED see H.273

H.273
22.03.67

T Mk10, Mk22, 22A

Controls: To Introduce Flap Control Lever Quadrant Assembly Part No. C1–CF 731A/2 in Lieu and by Conversion of C1-CF 731A/1

H.274
21.03.67
T Mk10

Fuel System: Installation of Fuel Filter Type LF1/3 (Hymatic). CANCELLED

H.275
27.06.67
T Mk10
Civil Series

Alighting Gear: To Introduce Special Bolt Part No. C1-UT 199 in Lieu of Standard Bolt A.25-66G on

Tailwheel Yoke with Glider Towing Attachment

H.276
12.01.68
T Mk10
Civil Series

To Introduce Tailcone Assembly Part No. C1-FS1801A in Lieu and by Conversion of Part No. C1-FS 647A/1

H.277
12.01.68
T Mk10
Civil Series

Engine Installation: To Introduce Rear Manifold Assembly Part No. C1-E99A/ND and Clip Part No.

C1-EE 101 in Lieu of Rear Manifold Assembly Part No. C1-EE 81A/ND. Part A: New Manufacture. Part B: Retrospective Action

H.278
26.03.68
T Mk10
Civil Series

Fuselage: To Introduce Tailcone Assembly Part No. C1-FS 1871A/ND in Lieu and by Conversion of Part No. C1-FS 158A/ND

H.279
01.68
T Mk10

Alighting Gear: To Introduce Mainwheel AH51981 in lieu and by Conversion of AH9389. Dunlop

Modification 4179. CANCELLED

H.280
20.10.69

T Mk10, Mk22, 22A

Controls: To Introduce Cable Guard Part No. C1-CF 1507A in Lieu of Cable Guard Part No. C1-CF 1171

H.281
24.05.68
Civil Series
T Mk10

To Introduce Reinforced Ribs and Modified Rib to Front Spar Attachment Angles in Centre Tailplane

Structure

H.282
05.09.68
Civil Series
T Mk10

Fuselage: To Introduce Attachment of Fire Extinguisher Mounting Bracket

H.283
24.10.68

Civil Series T Mk10

Fin: To Introduce Rib Support Angle C1-TF 101A in Lieu of C1-TF 35A. Part A: New Production. Part B: Retrospective Action

H.284
01.11.68
Civil Series
T Mk10

Fuselage: To Introduce a Strengthened Lower Portion of Former No. 1 Part No. C1-FS.1821 in Lieu

of C1-FS 319

H.285
12.11.68

T Mk10, Mk22, 22A

Engine Installation: To Re-run the Slow Running Cut-off Cable and Re-position the Pull Ring Mounting Bracket. Part A: Pre Mod H.263. Part B: Post Mod H.263

H.286
02.04.69
Civil Series
T Mk10

Oil System: To Introduce Oil Tank Part No. C1-LT 347A in Lieu and by Conversion of C1-LT 323A

H.287



Not Allocated

H.288
26.06.69
T Mk10
Civil Series

Fuselage: To Introduce a Steel Tie Bar in Lieu of a Light Alloy Tie Bar at Bottom Boom of Centre Section Spar

H.289
26.06.69
T Mk10
Civil Series

Aerofoils: To Introduce Steel Wing Root Insert Fittings in Lieu of Light Alloy Fittings at Bottom Boom of Wing

H.290
26.06.69
T Mk10
Civil Series

Aerofoils: Replacement of Inboard Portion of Lower Spar Boom

H.291
11.08.69

T Mk10, Mk22, 22A

Electrical Equipment: To Introduce a Remote trimmer Resistance Ref: No. 5UC/5210 in Lieu of 5UC/5780 in the Voltage Regulator Circuit

H.292
31.10.69
T Mk10, Mk20,
21, 22, 22A

Fuselage, Cockpit: To Make Provision for Restraint Harness Part No. MRI-GQ716 in Front Cockpit

and MRI-GQ729 in Rear Cockpit in Lieu of 6F/246 (Front) and 6F/245 (Rear)

H.293
24.06.70
T Mk10

Airframe: To Introduce Modified External Paint Scheme

H.294
10.07.72

T Mk10, Mk20, 21, 22, 22A

Aerofoils: To Introduce Rudder Part No. C1-TR 157A/2 in Lieu and by Conversion of C1-TR 157A/1

H.295
10.07.72
T Mk10, Mk20,
21, 22, 22A

Aerofoils: To Introduce Elevator Part No. C1-TE-1/3 in Lieu and Conversion of C1-TE-1/2 and C1-

TE-2/2

H.296
11.03.71
T Mk10

Controls: To Introduce Rear Rudder Bar Assembly Part No. C1-CF 69A/4 in Lieu and by Conversion of C1-CF 69A/3

H.297
19.10.70
T Mk10
Civil Series

Engine Installation: To Introduce Adjusting Sleeve Part No. C1-E573 in Lieu of Part No. C1-E 162

for Engine Mounting Rear Foot

H.298
13.10.70
T Mk10

Miscellaneous: To Introduce Improved Protection to the Fuselage Battery Compartment. Withdrawn in Favour of H.309

H.299


T Mk10,
Mk22, 22A

Engine Installation: To Introduce Revised End Connections for Carburettor Hot/Cold Air Control

Cables

H.300
21.06.71
T Mk10,
Mk22, 22A

External Finish: To Introduce Revised External Colouring and NATO Markings for Royal Navy

Aircraft (superseding Mod H.271)

H.301
24.02.72
T Mk10,
Mk22, 22A

Flying Controls: To Introduce Larger Diameter Pulley Part No. C1-CF.271 for Flap Control Cable at

Wing Root Rib

H.302
04.02.72

T Mk10, Mk22, 22A

Engine Installation: To Reposition the Engine Speed Indication Generator (A/780) to Provide Improved Routing of Flexible Drive (6A/1504) (Superseding Mod H.82 for Mk.10)

H.303
01.03.72
Mk21, 22, 22A

To Introduce a Warning Indication of Starter Relay Failure (Post H.85)

H.304
17.03.72
T Mk10

Electrical: To Introduce Battery Type J Ref No 5J/9496080 in lieu of Type C ref no 5J/3200. Superseded by Modification H.309

H.305


Mk20, 21, 22,
22A

To Introduce 2 Monobloc Battery Sections (Varley Part No. 12 19/25) in Lieu of Batteries Type C

H.306


T Mk10, Mk20, 21, 22, 22A

Flying Controls: To Introduce Rudder Control Hinge Bracket Part No. C1-TF 71/1 in Lieu of C1-TF 71

H.307
15.05.72
T Mk10,
Mk22, 22A

External Finish: To Introduce Revised External Colour Scheme (Red/White/Grey)

H.308
15.05.72
T Mk10

Electrical: Introduction of Revised Wiring. CANCELLED

H.309
26.06.72

T Mk10, Mk22, 22A

Fuselage Structure: To Make Provision for and Introduce Battery Type J in Lieu of Battery Type C by Extending the Battery Compartment (Enhanced Version of Civil Modification H.305)

H.310
12.10.72
Mk20, 21, 22,
22A

Wings: To Introduce Undercarriage Leg Mounting Casting Part No. C1.W 1023 and C1.W 1024 in

Lieu of Part No. C1-W 639 and C1-W 640

H.311
15.12.72

T Mk10, Mk22, 22A

Fuel System: To Introduce Drain Valve Vickers Type A.5268 Mk.B in Lieu of Plug Part No. 4 PT 123 for the Fuel Tank Sump Drain

H.312
11.01.73
T Mk10, Mk20,
21, 22, 22A

Fuselage: To Introduce Reinforcement to Former at Lower Cowling Attachment Bracket (Post

Modification H.284)

H.313
15.01.73

T Mk10

RN Only

Radio: Introduction of PTR 170 UHF. Covered by Modification H.263

H.314
15.01.73

Mk20, 21, 22, 22A

To Introduce Hoffmann Wood Propeller Part No. HO 21HM 198B/140L, Spinner Part No. FP 3037 and Back Plate Part No.3038 in Lieu of Fairey Metal Propeller etc.

H.315
16.05.73
T Mk10,
Mk22, 22A

Miscellaneous: To Introduce a Guard for the Rear Cockpit Ignition Switches

H.316
08.06.73
T Mk10,
Mk22, 22A

Radio: To Introduce Connector Type 10318 for Mic-tel Headsets and to Delete Redundant Socket

Type 359

H.317
20.07.73

Mk22, for ac

C1-0001 only

To Introduce New Tailwheel Two-track Tyre (Part No. Dunlop DA 2435) in Lieu of Existing Part No.

DS 13420

H.318
23.08.73
T Mk10

Introduction of Shell Fuel Carnet Holder. Requirement Withdrawn by MOD

H.319
31.08.73
T Mk10,
Mk22, 22A

Miscellaneous- To Introduce Accelerometer to Front Cockpit Coaming

H.320
20.09.73
T Mk10,
Mk22, 22A

Fuselage – To Make the Glider Tow Facilities Quickly Detachable

H.321
05.11.73
Mk 22

Introduce Collins 618-1C VHF Radio Equipment in Lieu of Type STR 9X Equipment

H.322
26.07.74
T Mk10

Engine Installation: To Introduce Angled Fairlead Pt No C1-E585A in lieu of Straight Fairlead Pt No

C1-E575A for ESI Flexible Drive. Incorporated with Modification H.302

H.323
17.02.75

T Mk10, Mk20, 21, 22, 22A

To Introduce Aerobatics and Spin Prohibited Label (Pre-Modification H.231)

H.324
17.02.75
T Mk10, Mk20,
21, 22, 22A

To Introduce Spin Recovery Advisory Label (Post-Modification H.231)

H.325
16.05.75

T Mk10, Mk22, 22A

To Introduce Pitot-static Pipe Clipping in Rear Cockpit

H.326
24.07.75
Mk22
G-BARS

To Introduce Structural and Electrical Changes to Modification H.321 To Suit Aircraft C1-0557

H.327
10.10.75
T Mk10

Radio: To Introduce a Press-to-Mute Facility in the Front Cockpit

H.328
12.01.76

T Mk10, Mk22, 22A

To Introduce Velcro Fastening to Ends of Adjustable Shoulder Straps in Lieu of Stitching

H.329
23.01.76
T Mk10,
Mk22, 22A

To Introduce Bendix RT 221 with VHF TR 1936 B Retained

H.330
16.02.76
Mk22

Beacons: To Introduce Whelen Strobe–type A413 HD Anti-Collision Light

H.331
05.10.76

Mk22 (G-BARS)

To Introduce Collins 20 VHF Radio Equipment in Lieu of 618F-1C Equipment

H.332
20.10.76
T Mk10,
Mk22, 22A

To Introduce VHF Communications Equipment Marconi AD120 in Lieu of Existing TR 1900 Series

Equipment

H.333
07.07.77
T Mk10

External Finish: To Introduce Colour Coding and Symbols at Fuel Filler Cap Positions and Revised Colours for Propeller. CANCELLED.

H.334
14.07.77
Mk22

To Introduce I/C-R/T Switches on Control Columns

H.335
23.06.78
T Mk10
(AAC Only)

To Introduce UHF Stand-by Radio D403 (ARI 23159). Part A: Fixed Fittings. Part B: Removable

Fittings

H.336
18.06.79

T Mk10, Mk22, 22A

Fuselage: To Introduce Cockpit Heating by the Installation of Warm Air Ducting

H.337
18.04.80
T Mk10,
Mk22, 22A

Radio: To Introduce Plessey PTR 1751 ARI 23301/26 UHF in Lieu of PTR 170 ARI 18197/1 UHF

H.338
18.04.80

T Mk10, Mk22, 22A

To Introduce Acrylic Paint Finish to DTD 5599A on External Metal Surfaces

H.339
27.06.80
T Mk10,
Mk22, 22A

Flying Controls: To Introduce Flap Control Cables Part Nos. SP 53-0570-16, SP 53-0520-23 and SP

530520-20 25 in Lieu of Part Nos. AS 1387-16, AS 1406-23 and AS1406-20

H.340
11.07.80

T Mk10, Mk22, 22A

To Introduce and Make Provision for Battery Type J Ref: 5J/65466954 in Lieu of Battery Type J Ref: 5J/3496080 and to Introduce Vent Adaptor Banjo

H.341
08.12.80

T Mk10, AAC ac WP983

& WZ884 only

To Introduce and Make Provision for a Mk. 14 Fatigue Meter and Air Speed Switch (6A/446 4239) and Air Speed Switch (6A/11453)

H.342
14.01.81
T Mk10

To Introduce Cleveland Wheels and Brakes in lieu of Dunlop Items. CANCELLED by the MOD

H.343
03.04.81
T Mk10
(except AAC)

To Introduce an Extended Front Cockpit Coaming (Concurrent with Mod. H.337). CANCELLED

H.344


T Mk10

To Introduce Chelton Broad Band UHF Antenna Type 16-1 (Ref: 10B/2222-399) in Lieu of McMichael UHF Aerial Type

H.345
31.07.81
T Mk10,
Mk22, 22A

To Introduce an Aerial Bonding Post in the Starboard Wing (Complementary to H.332)

H.346
10.11.81
T Mk10

Undercarriage: To Introduce Revised Dunlop Brake Units. Withdrawn by MOD

H.347
12.01.82
T Mk10

To Introduce Top Rear Canopy Rail Part No. C1.FC.817 in Lieu of C1.CF.623 and Side Rails Part No. C1.FS.1905-6 in Lieu of C1.FS.621-2 (Future Spares Only)

H.348
10.03.82
T Mk10

Fuel System: To Introduce Replacement Fuel Filler Cap Retaining Chain.

CANCELLED by MOD

H.349
04.06.82
T Mk 10,
Mk20, 21, 22, 22A

To Delete the Induction Manifold Heater Pipes and Blank Off Exhaust Manifold.

Part A: RN ac Pre-Mod. H.336, Civil ac Pre-Mod. H.354. Part B: AAC/RAF ac Post Mod. H.336, Civil ac Post-Mod. H.354

H.350
14.07.82

T Mk10, Mk20, 21, 22, 22A

To Introduce Safety Catch for the Fuel Cock Control Lever (Front Cockpit Only)

H.351
27.09.82
T Mk10

Undercarriage: To Introduce Torque Plate AHM8280 (Dunlop Mod. M1540)

H.352
08.03.83
T Mk10,
Mk22, 22A

To Introduce Rudder Pedal Assembly C1-CF 1537A and 1538A in Lieu and by Conversion of

Assembly C1-CF 1373A

H.353
09.03.83
T Mk 10

To Make Provision for Carriage of 2 Spare Parachutes and Helmets

H.354
13.05.83
Mk20, 21, 22,
22A

Fuselage: To Introduce Cockpit Heating by the Installation of Warm Air Ducting

H.355
13.06.83
T Mk10

To Introduce New Control Cables for the Cockpit Heating. Incorporated with Modification H.336

H.356
30.06.83

T Mk10,

Mk22, 22A

Fuselage: To Introduce “No Step” Markings on the Cockpit Control Box Covers

H.357
11.07.83

T Mk10, Mk20, 21, 22, 22A

To Introduce Tailplane Attachment Fitting Part No. C1-TP 313 in Lieu of Fitting C1-TP 167

H.358
10.10.83
T Mk10, Mk20,
21, 22, 22A

Fuselage: To Introduce Reinforcing Plates at the Upper Engine Mounting Attachment Points

H.359
10.10.83

T Mk10, Mk20, 21, 22, 22A

Mainplanes: To Introduce Inspection Access Holes Adjacent to the Undercarriage Mounting

H.360
10.10.83
T Mk10, Mk20,
21, 22, 22A

To Introduce Reinforcing Strips to Each of the Flanges of the Fin Rear Spar: Part A: Aircraft Pre-

mod H.178. Part B: Aircraft Post-mod H.178

H.361
10.10.83
T Mk10

To Withdraw Aircraft Serial Number Markings from Underside of Wings. CANCELLED by MOD

H.362
13.03.84
T Mk10 (AAC)

Radio: To Introduce Plessey PTR 1751 UHF in Lieu of PTR 170 UHF (ASR 889)

H.363
03.08.84

T Mk10, Mk22, 22A

Fuselage: To Introduce a Sealing Gasket CIFS 1909 ND at the Brake Cylinder Access Panel. Access Panel Part No. CIFS 1079 ND Becomes CIFS 1907A

H.364
15.11.84
T Mk 10
(RAF only) Mk22, 22A

Instruments: To Introduce Air Path Type C 2400-L4PS Compass in Lieu of Compass Type E2B on the Cockpit Coaming

H.365
19.08.85
T Mk 10
(RAF only) Mk22, 22A

Communications: To Make Provision for and Introduce UHF Radio ARI 23301/56 (25KHz) in Lieu of and by Conversion of UHF Radio ARI 23301/26 (50 Khz)

H.366
24.06.86
T Mk10

Electrical: Cover modification for repair of Generator to Suppressor Cable Part No. C1-N177A. See

SEM/Chipmunk/20. No leaflet issued.

H.367
01.05.87
T Mk10 (RN)

Communications: To Introduce VHF Radio AD 120 in Lieu of UHF Radio PTR 170 and Standby Bendix VHF

H.368
25.08.87
T Mk10

Electrical: To Introduce GatesVarley Sealed Lead Acid Battery Part No. 9750-0741 in Lieu of Varley

J Type Battery Part No.V2092

H.369
21.04.88
Mk22
(G-BARS & G-BBRV)

Communications: To Introduce Becker Radio AR3201-(1) VHF Radio in Lieu of Type STR 9X Equipment

H.370
31.08.88
T Mk10
(AAC only)

Communications: To Introduce UHF Radio ARI 23291/12 (25KHz) in Lieu of UHF Radio ARI 2391/2 (50KHz)

H.371
20.10.88

T Mk10 (RAF & AAC)

Electrical: To Introduce Conspicuity Strobe Lights on the Wing Tips. Part A: Fixed Fittings in Mainplanes. Part B: Fixed Fittings in Fuselage. Part C: Removable Equipment – Hella HISL, Power

Supply and Wiring

H.372
12.12.88

T Mk10

(RN only)

Communications: VHF Radio – To Introduce Wiring Changes Necessary to Permit Dual Installation (AD 120/RT221)

H.373
15.12.88
Mk22 (SOO)

Electrical: Battery – Concord batteries CB 12-9 (2 off) Fitted in Lieu of Batteries Type J (Mod H.309)

H.374
27.04.89
T Mk10,
Mk22, 22A

Flying Controls: Flaps – To Introduce a Revised Method of Assembly for the Flap Control Cable

Swivel Pulley Installation at the Wing Root

H.375
22.05.90
Civil Series: Mk20, 21, 22,
22A, 23

Flying Controls: Flaps – To Introduce a Revised Method of Assembly for the Flap Control Cable Swivel Pulley Installation at the Wing Root

H.376
24.01.91

TMk10, Mk22, 22A

Instrumentation: To Introduce Fuel Contents Gauge PW1335FG in Lieu and by Conversion of Type LV1335FG. Cover Mod for Smiths Mod SIB 1671

H.377
23.07.91
T Mk10,
Mk22, 22A

To Introduce Rotax Electric Starter in Lieu of Coffman Cartridge Starter

H.378
14.07.92

T Mk10, Mk 20, 21, 22,

22A, 23

Undercarriage: To Introduce Undercarriage Piston Tube C1-U-179A in Lieu of Piston Tube C1-U-55

H.379
02.11.93
T Mk10 (AAC)

Communications: Relocation of Disable Switch for PTR1751BB Radio (SRIM 4223)

H.380
20.04.95
T Mk10

Conversion of T Mk10 ac to Mk 22/22A. CANCELLED

H.381
22.02.96
T Mk 10 (SOO)

Fuel Management: To Make Provision for and Introduce 24 Gallon Fuselage Tank (Part No. C1-Z- 1673A), Associated Piping and Valves.

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