Aviation Alerts
Extracted From:
AC No. 43-16A
Alert No. 316
November 2004

Cessna; Model 172 Series (Model years 1956 through 1981) and Model 175 Series (Model years 1958 through 1962);
Horizontal Stabilizer Forward Spar; ATA 5510, 5511

The following article is published as it was received.

Maintenance technicians have found cracks in the forward horizontal stabilizer spar on Cessna 172 /175 series airplanes.

A search of the FAA Service Difficulty Reporting System database revealed 76 separate reports of these occurrences during the past 30 years.

Cessna Mandatory Service Bulletin No. SEB94-8 was released on April 29, 1994. The following quote is from the Purpose of this service bulletin:
“Service experience indicates the possibility of cracks/buckles developing in the area aft 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.” Cessna models 172R and 172S airplanes, built since 1996, incorporate the front spar reinforcement. NOTE: Improper ground handling can cause cracking and deformation of the horizontal stabilizer structure. It is recommended that a tow/steering 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.”

In addition, the Cessna service manual for 172 series airplanes states: “Caution: do not push on control surfaces or outboard empennage surfaces.”
The service manual also specifies inspection of the horizontal stabilizer spars each 100 hours for “cracks, wrinkles, loose rivets, corrosion or other damage”.

Adherence to Cessna Mandatory Service Bulletin No. SEB94-8 and to the Cessna Service Manual for 172 series airplanes is strongly recommended. Avoid steering these airplanes on the ground using the empennage.