2001-06-17: Engine Idle Speed and Fuel Control Mixture Setting

2001-06-17 CESSNA AIRCRAFT COMPANY: Amendment 39-12164; Docket No. 2001-CE-14-AD. (a) What airplanes are affected by this AD? This AD applies to Models 172R and 172S, all serial numbers, that are certificated in any category. (b) Who must comply with this AD? Anyone who wishes to operate any of the above airplanes must comply with this AD. (c) What problem does this AD address? The actions specified by this AD are intended to detect and correct an over-rich fuel mixture (improper fuel flow settings), which could result in rough engine operation or engine stoppage. This over-rich fuel mixture also contributes to the engine not restarting during flight when using published in-flight restart procedures. (d) What must I do to address this problem? To address this problem, you must accomplish the following actions: Action Compliance Time Special Instructions (1) Accomplish one of the following inspections for proper engine idle speed and fuel control mixture setting: (i) Pilot Procedure: Accomplish the inspection with the engine oil temperature between 120 and 150 degrees Fahrenheit (F). Assure that the engine idle setting is between 575 and 625 revolutions per minute (RPM) and the mixture setting will produce a minimum 10 RPM rise and a maximum 50 RPM rise with the throttle at the hard ground idle stop. Screw the vernier mixture out slowly counterclockwise to obtain the RPM rise. (ii) Mechanic Procedure: Accomplish the inspection with the engine oil temperature between 120 and 150 degrees F. Assure that the fuel mixture setting is between 575 and 625 RPM and the mixture setting will produce a minimum 10 RPM rise and a maximum 20 RPM rise with the throttle at the hard ground idle stop. Screw the vernier mixture out slowly counterclockwise. The reason the limits are different than the pilot procedure is that the mechanic needs to establish a more accurate RPM indicator than the airplanes engine RPM gage. You will most likelyneed to use an electric tachometer to verify speed changes. Within the next 10 hours time- in-service (TIS) after April 20, 2001(the effective date of this AD), unless already accomplished. The owner/operator holding at least a private pilot certificate as authorized by section 43.7 of the Federal Aviation Regulations (14 CFR 43.7) may accomplish the inspection specified in paragraph (d)(1)(i) of this AD. Make an entry into the aircraft records showing compliance with this portion of the AD in accordance with section 43.9 of the Federal Aviation Regulations (14 CFR 43.9). You may need to accomplish seasonal adjustments of the engine idle speed setting. These seasonal adjustments should not be included in your already established 12-month scheduled adjustments. (2) If, during any inspection required by this AD, proper engine idle speed and fuel control mixture setting cannot be met, accomplish the following: (i) Adjust the fuel servo. This adjustment or any replacementmust be accomplished by an appropriately- rated mechanic or at an appropriately- rated repair station; and (ii) Repeat the inspection specified in paragraph (d)(1) of this AD. Accomplish the adjustment (if required) prior to further flight after the inspection required by paragraph (d)(1) of this AD. Reinspect within 25 hours TIS after the fuel servo adjustment. If you have to adjust the servo more than twice over a 12-month period, obtain the next course of action from the FAA at the address referenced in paragraph (f) of this AD. We recommend you use an electronic strobe to verify RPM settings when making any adjustment. (3) Add the following information to the end of page 3-20, Section 3 Emergency Procedures of the Cessna 172R or 172S Pilot's Operating Handbook (POH) and FAA-approved Airplane Flight Manual (AFM): "IDLE POWER ENGINE ROUGHNESS An excessively rich idle fuel flow may cause low speed engine roughness during flight. During most in-flight low engine speeds (power off stalls, approach to landing, etc.), the mixture control is normally in the full-rich position. However, to improve engine roughness (caused by an improperly adjusted fuel servo) during low engine speeds while in flight, you should rotate the vernier mixture control (leaning of fuel mixture). You may also have to lean the fuel mixture if this low engine speed results in power loss and you need to restart the engine during flight. In all cases, you should land the airplane at the nearest airport for repairs if low speed engine roughness requires you to adjust the fuel mixture control to improve engine operation." Within the next 10 hours TIS after April 20, 2001 (the effective date of this AD), unless already accomplished. The owner/operator holding at least a private pilot certificate as authorized by section 43.7 of the Federal Aviation Regulations (14 CFR 43.7) may insert the information into the POH as specified in paragraph (d)(3) of this AD. You may insert a copy of this AD into the appropriate sections of the POH to comply with this action. Make an entry into the aircraft records showing compliance with portion of the AD in accordance with section 43.9 of the Federal Aviation Regulations (14 CFR 43.9). (4) Insert the following information into the applicable Cessna Pilot's Operating Handbook (POH) and FAA-approved Airplane Flight Manual (AFM): "NORMAL PROCEDURES (Before Takeoff) item 13. Throttle: 1. Verify smooth engine operation at idle speed of 575 to 625 RPM. 2. 1000 RPM or LESS" Within the next 10 hours TIS after April 20, 2001 (the effective date of this AD), unless already accomplished. The owner/operator holding at least a private pilot certificate as authorized by section 43.7 of the Federal Aviation Regulations (14 CFR 43.7) may insert the information into the POH as specified in paragraph (d)(4) of this AD. You may insert a copy of this AD into the appropriate sections of the POH to comply with this action. Make an entry into the aircraft records showing compliance with portion of the AD in accordance with section 43.9 of the Federal Aviation Regulations (14 CFR 43.9). (e) Can I comply with this AD in any other way? You may use an alternative method of compliance or adjust the compliance time if: (1) Your alternative method of compliance provides an equivalent level of safety; and (2) The Manager, Wichita Aircraft Certification Office (ACO), approves your alternative. Submit your request through an FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, Wichita ACO. Note: This AD applies to each airplane identified in paragraph (a) of this AD, regardless of whether it has been modified, altered, or repaired in the area subject to the requirements of this AD. For airplanes that have been modified, altered, or repaired so that the performance of the requirements of this AD is affected, the owner/operator must request approval for an alternative method of compliance in accordance with paragraph (e) of this AD. The request should include an assessment of the effect of the modification, alteration, or repair on the unsafe condition addressed by this AD; and, if you have not eliminated the unsafe condition, specific actions you propose to address it. (f) Where can I get information about any already-approved alternative methods of compliance? Contact Mr. Paul Pendleton, Aerospace Engineer, Wichita Aircraft Certification Office, FAA, 1801 Airport Road, Mid-Continent Airport, Wichita, Kansas 67209; telephone: (316) 946-4143; facsimile: (316) 946-4407. (g) What if I need to fly the airplane to another location to comply with this AD? The FAA can issue a special flight permit under sections 21.197 and 21.199 of the Federal Aviation Regulations (14 CFR 21.197 and 21.199) to operate your airplane to a location where you can accomplish the requirements of this AD. (h) When does this amendment become effective? This amendment becomes effective on April 20, 2001.