Single Engine Service Bulletin April 29, 1994 SEB94-8 TITLE HORIZONTAL STABILIZER FORWARD SPAR INSPECTION/MODIFICATION EFFECTIVITY Model Series Year Serial Numbers 172 1956 thru 1960 28000 thu 47746 172 1961 thru 1986 ‘7ea7747 thru 17278673 172 (141A) 1965 thru 1969 17251947 thru 17259015 172RG 1980 thru 1985 172RGO001 thu 172RG1191 FI72 1968 thru 1969 F172-0001 thru F172-0654 Fi72 1970 thru 1986 F17200855 thru F17202254 R172 (T41B,C,D) _—_1967 thru 1969 172.0001 thru 172.0409 R172 (Ta1C,0) 41970 thru 1975 1720410 thru R1720625 R172 1977 thru 1981 1722000 thru-A1723454 FRI72 41968 thru 1981 FR17200001 thru FR17200675 Pi72 1963, 17257120 thu 17257188 FP172 1963, FP172-0001 thru FP172-0003 178 1958 thru 1960 55001 thru 6777 175 1961 thru 1962 17556778 thru 17557119 PURPOSE ‘Service experience indicates the possibilty of cracks/buckles developing in the area of the center lightening hole in the horizontal stabilizer forward spar. An inspection for cracksibuckles in this area should be conducted. If a crack or buckle is found, the spar shall be repaired or replaced depending upon the extent of crack propagation. To assist in preventing this condition from occurring, a new strengthened one-piece forward spar reinforcement is available. Non-compliance with this service bulletin may result in failure of the horizontal stabilizer. NOTE: Improper ground handling can cause cracking and deformation of the horizontal stabilizer structure. Itis recommended that a tow/steoring bar be used whenever the airplane is to be manually positioned on the ground. Do not steer the airplane by pushing down on the horizontal stabilizer. Page 1 of 3 To obiain satstactory results, procedures speciiod in this pubicaton must be accomplished in accordance with accepted mthods and prevaling goverment regulabons. The Cessna Aircraft Company cannot be responsible for the quay of work performed in ‘ccamplshing the requirements ofthis publication. ‘The Cossna Arcratt Company rode! Support PO. Bax 7708, Wet, Kanes 7277, US. (216) 94.7860, Facsimile 316) 942.008 COPYRIGHT © 1994COMPLIANCE Mandatory: ‘A. Initial Inspection: Shall be inspected within the next 100 hours of operation or 12 months, whichever occurs fist. B. Repetitive inspections: Accomplish every 100 hours of operation or 12 months after the initial inspection until installation of part number 0531037-1 horizontal spar reinforcement or 0532001-98 horizontal stabilizer forward spar. APPROVAL FAA approval has been obtained on technical data in this publication that affects airplane type design. For Reims Aviation airplanes; DGAC approval has been obtained on technical data in this publication that affects airplane type design MAN-HOURS ‘Approximately 0.6 man-hours to inspect the horizontal stabilizer forward spar ‘Approximately 14.0 man-hours per airplane to install a 0531037-1 forward spar reinforcement. Forward spar assembly replacement, not determined. MATERIAL, ‘The following parts are available from Cessna Parts Distribution thru an appropriate Cessna Service Station for the suggested list price shown. Part Number Description Qty/Airplane Price 0531037-1 Reinforcement - 1 $ 32.80 (S) ea Forward Spar {f Required 0532001-23 Center Skin - 1 $ 80.10 (S)ea. Horizontal Stabilizer If Required 0532001-98 Forward Spar Assembly - 1 $ 271.00 (S) ea. (See Note) Horizontal Stabilizer f Required MS20426AD4-4 Rivet 10 $ 23.00 (PS) Ib. f Required MS20426AD4-6 Rivet 6 $ 18.90 (PS) Ib. if Required MS20470AD3-3 Rivet ‘As Required $ 30.70 (PS) Ib. MS20470AD3-4 Rivet 10 $ 23.30 (PS) Ib. If Required MS20470AD4-4 Rivet 8 $ 16.50 (PS) Ib. If Required NOTE: 0532001-98 horizontal stabilizer forward spar assemblies incorporate the 0531037-1 reinforcement. ~ ALL PRICES SUBJECT TO CHANGE WITHOUT NOTICE SEB94-8 Page 2 April 29, 1994CREDIT Not applicable. ACCOMPLISHMENT INSTRUCTIONS. Horizontal Stabilizer Forward Spar Inspection/Moditication Accomplishment instructions are attached. OWNER NOTIFICATION On April 29, 1994 the following Owner Advisory message will be sent to applicable owners of record in SEB94-8A. Dear Cessna Owner: Service experience indicates the possibility of cracks/buckles developing in the area of the center lightening hole in the horizontal stabilizer forward spar. An inspection for cracks/buckles in this area should be conducted. If a crack or buckle is found, the spar shall be repaired or replaced depending upon the extent of crack propagation. To assist in preventing this condition from occurring, a new strengthened one- piece forward spar reinforcement is available. Non-compliance with this service bulletin may result in failure of the horizontal stabilizer. Nor! Improper ground handling can cause cracking and deformation of the horizontal stabilizer structure. It is recommended that a tow’steering bar be used whenevor the airplane is to be ‘manually positioned on the ground. Do not steer the airplane by pushing down on the horizontal stabilizer. Compliance is mandatory: ‘A. Inital inspection: Shall be inspected within the next 100 hours of operation or 12 months, whichever occurs first. B. Repetitive Inspections: Accomplish every 100 hours of operation or 12 months after the initial inspection until installation of part number 0531037-1 horizontal spar reinforcement or 0532001-98 horizontal stabilizer forward spar. Please contact a Cessna Single Engine Service Station for detailed information regarding the accomplishment of this Service Bulletin on your airplane. SEBO4-8 April 29, 1994 Page 3ACCOMPLISHMENT ma Single-Engine INSTRUCTIONS of SEB94-8 TITLE — HORIZONTAL STABILIZER FORWARD SPAR INSPECTION/MODIFICATION EFFECTIVITY MODEL(s) ‘SERIAL NUMBERS 172 28000 thru 17276673 172 (T41A) 17251947 thru 17259015 R172 (T41B, C, D) 172-0001 thru R1720625 R172 1722000 thru R1723454 172RG 172RG0001 thru 172RG1191 F172 172-0001 thru 17202254 FRI72 FR17200001 thru FR17200675 FP172 FP172-0001 thru FP172-0003 172 17257120 thru P17257188 178 ‘65001 thru 17557119 DESCRIPTION To inspect the horizontal stabilizer forward spar for cracks at the center lightening hole and install a ‘one-piece reinforcement in the stabilizer forward spar. APPROVAL, FAA approval has been obtained on technical data in this publication that affects airplane type design. For Reims Aviation aitplanes: DGAC approval has been obtained on technical data in this publication that affects airplane type design. REFERENCE SEBO4-8 CHANGE IN WEIGHT AND BALANCE MODEL eee Al Models) WEIGHT INCREASE ............ 0.1 Pounds ARM eee tee 210.0/inches RESULTANT MOMENT .......... 21.0 Inch-Pounds MOMENT/1000 ................ 0.021 April 29, 1994 Page 1 of 8 To obtain satisfactory results, procedures specitied in this publication must be accomplished in accordance wih accepted methods and prevaling goverment rogulations. The Cossna Aicraf Company cannot bo responsible for tho quay of work performed in ‘ecomplshing he requirements ofthis publication, ‘The Cossna Alcraft Company rot Support, P.O Hox 770, Wet, Koss 6727, USA. (16) 7550, Fase S16 942-008 COPYRIGHT © 1994ACCOMPLISHMENT INSTRUCTIONS SEB94-8 MATERIAL INFORMATION NOTE: The following parts will be required to modify the horizontal stabilizer forward spar: PARTNUMBER QUANTITY DESCRIPTION 05310371 1 Reinforcement. Forward Spar MS20426AD4-4 10 Rivet-Reinforcement attach MS20426AD4-6 6 Rivet-Rib to Spar attach MS20470AD3-3 ‘As Required Rivet-Skin Attach MS20470AD3-4 10 Rivet-Reinforcement attach MS20470AD4-4 8 Rivet-Reinforcement attach NOTE: in addition to the parts listed above, the following components may be required to complete this modification: PART NUMBER QUANTITY DESCRIPTION 0532001-98 1 ‘Spar Assembly- Forward (if Required) Horizontal Stabilizer 052300123 1 ‘Skin-Center Horizontal (if Required) Stabilizer ACCOMPLISHMENT INSTRUCTIONS. 1. (Refer to Figure 1,) Inspection of the horizontal stabilizer forward spar: ‘A.__Display @ maintenance tag in the cabin in full view stating WARNING: DO NOT OPERATE AIRPLANE - MAINTENANCE IN PROGRESS B. Remove the fuselage-to-stabilizer aerodynamic fairings. Retain fairings and attaching hardware for reinstallation. C. Using a flashlight and an inspection mirror, locate the center lightening hole of the forward spar in the horizontal stabilizer. (1) (Refer to Figure 1, Sheet 3, View C-C.) From the aft side of the horizontal forward spar, ‘examine the centerline lightening hole for cracks. Cracks will generally radiate diagonally from the lightening hole. (2) cracks are present: (@) Cracks that have not progressed past the centerline lightening hole flange may be blended out. (0) Cracks that have progressed past the centerline lightening hole flange but do not extend to the spar flange radius, stop dril using a Number 30 (0.128 inch diameter) dri. Proceed to step 2. (©) Cracks that have progressed to the spar flange radius, replace the spar with a 0532001-98 forward spar assembly. Refer to step 2 of these instructions and the applicable airplane service manual. Page 2ACCOMPLISHMENT INSTRUCTIONS SEB94-8 (3) If no cracks are present: (a) If the 0531037-1 forward spar reinforcement is to be installed, proceed to step 2. (b) If the 0531037-1 forward spar reinforcement is not to be installed, proceed to step 3. (Refer to Figure 1.) Installation of the horizontal stabilizer forward spar reinforcement: ‘A. Block elevator trim tab actuator and cables to retain rigging. Do not remove the actuator, pulleys, or cables from the stabilizer. Label the cables for convenience of reinstallation B. Remove the horizontal stabilizer from the airplane. This procedure will include removing the rudder and the vertical fin. (Refer to Service Manual, Section 4, Wings and Empennage.) ©. Remove the fasteners securing the 0532001-28 stabilizer center skin, and remove the skin by sliding it forward. When driling out fasteners, note the type of fastener and location for reinstallation of the skin. D. Inspect the 0532001-23 skin for cracks: (1) Check the skin centerline lightening hole for cracks. If cracks are present and extend beyond the centerline lightening hole, repair or replace the skin. Repair can be accomplished by trimming the damaged part at the forward bend radii and splicing in a like section of the web portion with upper and lower flanges overlapping the existing skin at the trim lines. (2) Skins that have minor cracking that does not extend beyond the flange of the centerline lightening hole may be repaired by blending out such cracking in the flange. (3) Any buckled areas of the skin should be straightened and inspected for cracking, (4) If cracking extends beyond the flange, replace the skin. E. (Refer to Figure 1. Detail B.) Drill out 6 rivets securing the leading edge skins to the spar on either the left and right upper or lower surfaces (not both), removing fasteners to pull the leading edge skins back for tool access. F. Drill out the rivets from the trailing edge of the horizontal stabilizer between the inboard and second rib outboard at BL 17.25. Also remove the rivets attaching the pulley bracket doublers to the top and bottom skins in this area. This will permit the skins to be pulled back for tool access. G. From inside the right side of stabilizer, drill out the rivets securing the trim cable pulley bracket to the inboard rib. Leave the cables routed through the lightening holes and pulleys. Pull the ribs and cables out of the way and secure them while working to ensure proper routing and rigging upon reassembly. H. Remove the fasteners securing the existing 0532001-11 reinforcements to the aft face of the forward spar. Remove and discard these reinforcements. |. Replace the forward spar if cracks are present that extend to the spar flange. Blend out any cracking limited to the lightening hole flange. Straighten any buckling found in the spar web. J. (Refer to Figure 1, Sheet 3, View C-C, and Sheet 4, Detail D) Locate the new 0531097-1 one- piece reinforcement (which replaces the two reinforcements removed in step G.) Install the spar ‘web rivets on the left side only in existing rivet locations. Deburr all holes. Providing edge distance is maintained, fasteners one size larger may be used as required to obtain good holes and fit. K. (Refer to Figure 1, Sheet 4, Detail D) Using a Number 30 (0.128 inch diameter) drill, add equally spaced holes for new fasteners between the rivets securing the reinforcement to the spar flanges and skins. All rivets in the spar web can be driven from inside the stabilizer and bucked on the front side. Leave the rivet holes in the flange open where the center skin will attach. L._ Reeattach the leading edge skin using MS20470AD3-3 rivets. M. Locate and position the inboard ribs. Working through the loose stabilizer skin (along the aft spar), reattach the trim cable pulley bracket ensuring the cables are properly routed. Page 3ACCOMPLISHMENT INSTRUCTIONS SEB94-8 N. Reattach the stabilizer skin along the trailing edge using MS20470AD3-3 rivets. ©. Working through the lightening holes in the inboard ribs, buck the fasteners that attach the pulley bracket doublers to the stabilizer skin P. Install the 0532001-23 stabilizer center skin using MS20470ADS-3 rivets in the same locations recorded in the removal process. Q. Reinstall the stabilizer, vertical stabilizer, rudder, and elevators. Check the control riggings in accordance with the appropriate service manual 3. Make an entry in the airplane logbook stating this service bulletin has been accomplished and method of compliance, if applicable, note in the logbook when the next inspection is due. Page 4ACCOMPLISHMENT INSTRUCTIONS SEB94-8 STABILIZER LEADING EDGE (REFERENCE) STABILIZER FORWARD SPAR CENTER LIGHTENING HOLE (REFERENCE) pera A Figure 1. Horizontal Stabilizer Forward Spar Inspection’Modification (Sheet 1 of 4)ACCOMPLISHMENT INSTRUCTIONS SEB94-8 NOTE: LEADING EDGE NOT SHOWN FOR CLARITY ONLY. REMOVE 6 RIVET! AT THIS LOCATION BOTH LEFT AND RIGHT SIDE (REFERENCE) 0532001 SKIN (REMOVE AND RETAIN FOR REINSTALLATION IF peta B NO CRACKS ARE PRESENT. DISCARD EXISTING SKIN IF CRACKS ARE DETECTED. ‘AND INSTALL NEW SKIN.) Figure 1. Horizontal Stabilizer Forward Spar Inspection/Modification (Sheet 2) Page 6ACCOMPLISHMENT INSTRUCTIONS SEB94-8 REPLACE THE FORWARD SPAR IF CRACKS ARE PRESENT THAT EXTEND TO THE SPAR FLANGE RADIUS. HORIZONTAL STABILIZER HORIZONTAL STABILIZER CENTER D FORWARD SPAR-AFT LINE STRAIGHTEN ANY ‘SURFACE (REFERENCE) BUCKLING IN THE i SPAR WEB. =a Va nn i +l¢| + i. + INSPECT FOR CRACKS RADIATING DRILL OUT RIVETS FROM CENTER ‘SECURING EXISTING LIGHTENING HOLE. TWO 0532001 ‘STOP DRILL CRACKS REINFORCEMENTS. USING A NUMBER 30 REMOVE AND DISCARD (0.128 INCH DIAMETER) REINFORCEMENTS. OR LARGER DRILL BIT. BLEND OUT CRACKING LIMITED TO LIGHTENING HOLE FLANGE. view C-C (VIEW LOOKING FORWARD. AT AFT RIGHT SURFACE OF HORIZONTAL STABILIZER FORWARD SPAR) (LEFT SIDE TYPICAL) Figure 1. Horizontal Stabilizer Forward Spar Inspection/Modification (Sheet 3) Page 7ACCOMPLISHMENT INSTRUCTIONS ossr097-4. REINFORCEMENT MATCH DRILL TO HORIZONTAL (REFERENCE) EXISTING SPAR HOLES STABILIZER 0.098 INCH CENTER DIAMETER HOLE LINE (4 REQUIRED) 0.128 INCH DIAMETER HOLE (20 REQUIRED) MATCH DRILL TO EXISTING SPAR HOLES NUMBER 30 (0.128 INCH DIAMETER) (DIMENSIONS HOLE (6 REQUIRED) REFERENCE) peta D VIEW LOOKING FORWARD Figure 1. Horizontal Stabilizer Forward Spar nspection/Modification (Sheet 4) Page 8