MODIFICATION KIT CesSna 

~ A Textron eom;nv 

Single Engine 

MK172-28-01 

TITLE 

ENGINE FUEL RETURN SYSTEM INSTALLATION 

EFFECTIVITY 

DESCRIPTION 

Model 

172R 

172S 

Serial Numbers 

17280001 thru 17281187 

172S8001 thru 172S9490 

To provide parts and instructions to install the fuel return system modification. 

APPROVAL 

FAA approval has been obtained on technical data in this publication that affects airplane type design. 

REFERENCE 

SB04-28-03 

CHANGE IN WEIGHT AND BALANCE 

Model ............................. . 

Weight Change ...................... . 

ARM ............................. . 

Resultant Moment . . . . . . . . . . . . . . . . . . . . . 

Moment/1 000 

August 30, 2004 

172R/172S 

+1.0 Pound 

0 

0 

0 

Page 1 of 9 

To obtain satisfactory results, procedures specified in this publication must be accomplished in accordance with accepted methods and 

prevailing government regulations. Cessna Aircraft Company cannot be responsible for the quality of work performed in accomplishing the 

requirements of this publication. 

Cessna Aircraft Company, Product Support, P.O. Box 7706, Wichita, Kansas 67277, U.S.A. (316) 517-5800, Facsimile (316) 942-9006 

COPYRIGHT © 2004 
MATERIAL INFORMATION 

The following parts will be necessary: 

NEW P/N QUANTITY DESCRIPTION OLD P/N DISPOSITION 

MK172-28-01 1 Kit, consisting of the 

following parts: 

AE3663163E0240 1 Hose Assembly None None 

AN832-4 Union None None 

AN924-4 1 Nut None None 

MS21062L3 1 Nut None None 

MS2191WDG5 1 Clamp None None 

MS21929WDG10 1 Clamp None None 

MS35207 -264 Screw None None 

NAS1149F0332P 1 Washer None None 

MS29512-04 1 0-Ring MS29512-04 Discard 

S2218-4 1 Check Valve None None 

02G22973 1 Orificed Fitting Existing Plug Discard 

0500118-49 Line Assembly None None 

0500118-53 Line Assembly None None 

0516009-24 1 Fuel Reservoir Assembly 0516009-18 Discard 

MK172-28-01 Instructions 

In addition to the MK172-28-01 Kit, the following (or later revision) will be necessary. 

Part Number Description 

172RPHUSR09 Revision 9, Modei172R 

(See Note) Pilot's Operating Handbook 

172SPHUSR05 Revision 5, Modei172S 

(See Note) Pilot's Operating Handbook 

172R180PHUSR03 Revision 3, Model 172R 180HP 

(See Note) Pilot's Operating Handbook 

NOTE: This revision has been sent to applicable airplane owners of record. Refer to SB04-11-02 for detailed 

information. 

ACCOMPLISHMENT INSTRUCTIONS 

1 . Electrically ground the airplane and turn all switches to the "OFF" position. If external power is connected 

to the airplane, disconnect external power from receptacle. 

2. Disconnect the airplane battery. (Refer to the Model 172 Series 1996 and On Maintenance Manual, 

Chapter 24, Electrical Power.) 

3. Attach maintenance warning tags to the battery and external power receptacle with the following 

instruction: DO NOT CONNECT ELECTRICAL POWER - MAINTENANCE IN PROGRESS. 

4. Remove the upper and lower engine cowls. (Refer to the Model 172 Series 1996 and On Maintenance 

Manual, Chapter 71, Powerplant.) 

MK172-28-01 

Page2 
WARNING: DURING ALL FUEL SYSTEM SERVICING PROCEDURES, FIRE 

FIGHTING EQUIPMENT MUST BE AVAILABLE. TWO GROUND WIRES 

FROM TIE DOWN RINGS ON THE AIRPLANE TO APPROVED GROUND 

STAKES SHALL BE USED IN CASE OF ACCIDENTAL DISCONNECTION 

OF ONE GROUND WIRE. 

5. Defuel the airplane. (Refer to the Model 172 Series 1996 and On Maintenance Manual, Fuel - Servicing.) 

6. Remove the copilot seat and carpet. (Refer to Chapter 25, Front Seats and Rails - Maintenance Practices 

and Chapter 25, Interior Upholstery- Maintenance Practices.) 

A. Remove the copilot side 0515075-40 Panel to get to the fuel reservoir assembly. 

B. Remove the copilot side 0513512-9 Forward Floorboard and the access panel behind the rudder 

pedals to get to the fuel reservoir. 

7. (Refer to Figure 1.) Remove the safety wire and plug in the forward top side of the fuel servo and install a 

02G22973 Orificed Fitting with a MS29512-04 0-Ring. 

CAUTION: INSTALL A PROTECTIVE CAP ON THE ORIFICED FITTING UNTIL THE HOSE IS 

INSTALLED TO THE FITTING. 

CAUTION: BEFORE YOU DRILL INTO THE FIREWALL, MAKE SURE THAT THE AREA BEHIND 

THE FIREWALL, WHERE THE NEW HOLE WILL BE DRILLED, IS CLEAR OF ANY 

AIRPLANE STRUCTURE OR ANY OTHER ITEMS THAT MAY PREVENT THE 

INSTALLATION OF THE NEW FUEL LINE AND FITTINGS. 

8. (Refer to Figure 2, Sheet 1 and 2.) Drill 0.438 inch diameter fuel return hole in the firewall as shown. 

9. (Refer to Figure 3, Sheet 2.) Install a AN832-4 Union, NAS1149F0932P Washer, and AN924-4 Nut in 

the firewall fuel return hole as shown. 

10. (Refer to Figure 1, View A-A.) Install a AE3663163E0240 Hose Assembly between the fuel servo orificed 

fitting and the firewall AN832-4 Union. 

A. Remove the protective cap on the 02G22973 Orificed Fitting installed in Step 7 and install the 

AE3663163E0240 Hose Assembly nut to the orificed fitting. Leave the nut loose until the hose is 

positioned and clamped to the brace as shown. 

NOTE: The AE3663163E0240 Hose Assembly must be in a relaxed and smooth position before 

the nuts are tightened. 

B. Install the other end of the AE3663163E0240 Hose Assembly nut to the firewall AN832-4 Union. 

Leave the nut loose until the hose is positioned and clamped to the brace as shown. 

C. Attach the AE3663163E0240 Hose Assembly to the 0750625-4 Brace with clamps and hardware 

as shown. 

D. Tighten the AE3663163E0240 Hose Assembly nuts but make sure it is in a relaxed and smooth 

condition after the nuts are tightened. 

11. (Refer to Figure 3, Sheet 1.) Install the 0500118-49 Line Assembly from the aft side of the firewall 

AN832-4 Union to the S2218-4 Check Valve. Install the S2218-4 Check Valve and make sure the check 

valve flow arrow points to the reservoir. 

WARNING: BEFORE THE FUEL RESERVOIR IS REMOVED, MAKE SURE TO 

DRAIN THE FUEL FROM THE SUMP DRAIN ON THE RESERVOIR TO 

KEEP FUEL SPILLAGE TO A MINIMUM. 

12. Remove the 0516009-18 Fuel Reservoir Assembly that is installed in the airplane, keep all hardware. 

(Refer to the Model 172 Series 1996 and On Maintenance Manual, Chapter 28, Storage and DistributionMaintenance Practices.) 

13. Install a new 0516009-24 Fuel Reservoir Assembly into the airplane with the kept hardware. 

MK172-28-01 

Page3 
-----~-~----------------------- - --------------------~-------------- ------~-- ---

14. Install a new 0500118-53 Line Assembly from the aft end of the S2218-4 Check Valve to the new 

0516009-24 Fuel Reservoir Assembly. (Refer to the Model172 Series 1996 and On Maintenance Manual, 

Chapter 28, Storage and Distribution- Maintenance Practices.) 

15. Fuel the airplane and do a fuel leak inspection. 

16. Install the floorboards and the side panels removed in Step 6. 

CAUTION: MAKE SURE THE ATTACH SCREWS DO NOT TOUCH THE NEW INSTALLED FUEL 

LINE WHEN THE FLOORBOARDS AND ACCESS PANELS ARE INSTALLED. 

17. Install the copilot's seat and carpet. (Refer to Chapter 25, Front Seats and Rails - Maintenance Practices 

and Chapter 25, Interior Upholstery- Maintenance Practices.) 

18. Reconnect the airplane battery. (Refer to the Model 172 Series 1996 and On Maintenance Manual, 

Chapter 24, Electrical Power.) 

19. Install the upper and lower engine cowls. (Refer to the Model 172 Series 1996 and On Maintenance 

Manual, Chapter 71, Powerplant.) 

20. Remove maintenance warning tags from battery and external power receptacle. 

21. (Refer to the Pilot's Operating Handbook) Do a "before takeoff engine operation check". 

22. Put the applicable revision into the Pilot's Operating Handbook if it has not previously been incorporated. 

NOTE: Model 172R Pilot's Operating Handbook and FAA Approved Airplane Flight Manual, Revision 

9, or latest revision. 

Model 172S Pilot's Operating Handbook and FAA Approved Airplane Flight Manual, Revision 

5, or latest revision. 

Model 172R 180HP Pilot's Operating Handbook and FAA Approved Airplane Flight Manual, 

Revision 3, or latest revision. 

23. Make an entry in the airplane logbook that states this Modification Kit has been installed. 

MK172-28-01 

Page4 
MK172-28-01 

02G22973 

ORIFICED 

FITTING 

(1 REQUIRED) 

FUEL SERVO 

(REFERENCE) 

FIRE WALL 

(REFERENCE) 

I 

-------i 

-- I 

BRACE 

(REFERENCE) 

VIEW A-A 

MS21919WDG5 

CLAMP 

MS21919WDG10 

CLAMP 

MS35207-264 

SCREW 

I MS2102L3 

NUT 

NAS1149F0332P 

WASHER 

(1 EACH 

REQUIRED) 

AN832-4 

UNION 

(REFERENCE) 

AE3663163E0240 

HOSE 

ASSEMBLY 

(1 REQUIRED) 

0510T1007 

AA0550T359 

Figure 1 . Fuel Return System Installation (Sheet 1) 

Page5 
FIREWALL 

(REFERENCE) 

Page6 

DETAIL A 

Figure 2. Fuel Return Firewall Hole Installation (Sheet 1) 

0510T1007 

A0511T1008 

MK172-28-01 
83770 

FUEL 

STRAINER 

BRACKETS 

(REFERENCE) 

0.438 INCH DIAMETER 

FUEL RETURN HOLE 

(NOTE) 

+ 

/ 

/ 

CENTER 

LINE 

+ 

®·---® 

+ 

NOTE: 

LOWER FIREWALL;/' VIEW A-A 

j.-- 4.28 INCHES -----.J 

DOUBLER FLANGE LOOKING AFT 

(REFERENCE) LOWER FIREWALL ASSEMBLY 

DRILL A 0.438 INCH DIAMETER HOLE IN THE LOCATION SHOWN AND MAKE SURE YOU 

DO NOT DRILL INTO ANY OBSTRUCTIONS OR STRUCTURE ON THE 

AFT SIDE OF FIREWALL. 0553T031 

Figure 2. Fuel Return Firewall Hole Installation (Sheet 2) 

MK172-28-01 

Page? 
( 

A 

PageS 

A 

FUEL 

RESERVOIR 

(REFERENCE) 

/f 

A 

DETAIL A 

BEFORE FUEL RETURN MODIFICATION 

Figure 3. Fuel Return to Reservoir Installation (Sheet 1) 

0510T1007 

A0516T1007 

MK172-28-01 
83772 

FUEL 

STRAINER 

(REFERENCE) 

AE3663163E0240 

HOSE ASSEMBLY 

(REFERENCE) 

AN832-4 

UNION 

FIREWALL 

(REFERENCE) 

FUEL 

SHUTOFF 

VALVE 

(REFERENCE) 

ELECTRICAL 

FUEL 

PUMP 

(REFERENCE) 

AN924-4 0500118-49 

NUT LINE 

0516009-24 

FUEL 

RESERVOIR 

ASSEMBLY 

(1 REQUIRED) 

(1 REQUIRED) AN960-916L ASSEMBLY S2218-4 

CHECK VALVE 

(1 REQUIRED) 

MK172-28-01 

WASHER (1 REQUIRED) 

(1 EACH REQUIRED) 

~FWD 

VIEW A-A 

LOOKING DOWN 

AFTER FUEL RETURN MODIFICATION 

Figure 3. Fuel Return to Reservoir Installation (Sheet 2) 

050018-53 

LINE 

ASSEMBLY 

(1 REQUIRED 

0516T015DCN0498 

Page 9