Cessna 400 Series Aeroplanes

AD/CESSNA 400/40

Amdt 13

Applicability: All models.

Wing and Airframe 9/95

Requirement:  1. Retire the wing main spar lower cap and the upper and lower wing attachment fittings, before exceeding the component times in service or number of flights, whichever occurs first, as shown in the Retirement Schedule below.

2. The remainder of the airframe must be retired after the expiration of two wing lifetimes. Note 2 refers.

RETIREMENT SCHEDULE

Retirement Life

* Aircraft that have been modified in accordance with Hawker de Havilland Australia Ltd. Engineering Technical Instructions Nos 006 - 004 (models 402, 402A, 402B), 006 - 005 (402C), 006 - 006 (421A, 421B) or 006 - 007 (early 421C), and which are

subject to the related ongoing inspection program, are exempt from Requirement 1, the wing fatigue life limitation. The airframe life limitation of Requirement 2 still applies.

# Aircraft that are included in the Aeronautical Engineers Australia life extension program (AEA Engineering Order No E0971 for model 402), and which are subject to the related ongoing inspection program, are exempt from Requirement 2, but remain subject to any life limitations imposed by the Engineering Order. The wing life limitation of Requirement 1 still applies.

Note 1: The centre-section spar caps and attachment fittings are not affected by Requirement 1.

Note 2: The available fatigue data covers wing main spars only. The durability of other parts of the airframe has not been evaluated, and is therefore unknown. Based on experience, the Authority is prepared to credit unevaluated structure with a retirement life equal to double the life for the wing spar (Requirement 2). An extension beyond this may be available, but any application must be supported by a fatigue substantiation covering all the remaining primary structure. This should include empennage, wing centre section, wing rear spar, control surfaces, unpressurised fuselages, etc. The substantiation may take the form of a safe life assessment, or a sufficiently rigorous revised inspection schedule to ensure that any fatigue cracking which could occur in service will be detected before the aircraft is endangered. An example is the Aeronautical Engineers Australia life extension program for the model 402.

Note 3: For aircraft which have had winglets fitted subsequent to manufacture the Retirement Life, in hours and flights, is to be calculated using the formulae;

RF = A+RLW ( 1 -  A   )

RLW/O RF = B+RWF ( 1 -   B     )

RFW/O

Where

RL = Retirement Life (Hours) RF = Retirement Life (Flights)

A = Hours flown before winglets were fitted

B = Number of flights before winglets were fitted RLW = Retirement Life (Hours) with winglets fitted

RLW/O = Retirement Life (Hours) without winglets fitted RFW = Retirement Life (Flights) with winglets fitted RFW/O = Retirement Life (Flights) without winglets fitted

Note 4: To establish the number of flights accumulated, where such a record has not been kept, divide the number of flight hours accumulated by the average flight time given below:

Background:  The Retirement Lives promulgated in this Directive reflect the manufacturer’s latest fatigue analyses, which incorporate the results from fatigue tests. According to these best estimates, the risk of spar cracking increases to an unacceptable level beyond the specified life limitations. Only those models which use the non-redundant single main spar design are affected. This design makes it extremely difficult to develop a reliable and safe inspection program. In the absence of such an inspection program a life limitation must be imposed.

Amendment 8 included a number of changes:

(a)     Most lives were reduced. Except for the later production 421C models, the manufacturer’s fatigue tests of the “C” models have so far not demonstrated the longer fatigue lives that had been anticipated.

(b)     Some new models were added: the 414 and 414A, plus the “RAM” winglet conversions for the 414A and early 421C’s. The life limitations for the winglet aircraft are based on a simple, but conservative, analysis by a local consultant. A more detailed fatigue evaluation may yield a longer fatigue life.

(c)     “Average Cruise Weight” was replaced by “Average Ramp Weight” for the convenience of operators.

Amendment 9 extended the effectivity of the above changes by six months to1 May 1988, to give affected parties more planning time.

Amendment 10 exempted from the Requirement aircraft which incorporate certain life extension modifications. The list of approved modifications is not exhaustive as schemes are being developed to cover additional models. Details of schemes not listed can be obtained from the Authority.

Amendment 11 increased the retirement life for later production 414A aircraft. This results from a continued review of the 400 series lives, assisted by advice from the manufacturer. These aircraft are fitted with a heavier section spar assembly. The life for winglet aircraft is about half the life for the standard aircraft; the earlier comments in this Background still apply.

Amendment 12 reworded the Requirement paragraphs to make it clearer that the airframe life limit referred to in Note 2 applies to all aircraft, including those with the Hawker de Havilland spar modifications. The Aeronautical Engineers Australia life extension program for the model 402 has been included.

Amendment 13 aligns the retirement of the wing attachment fittings with retirement of the wing main spar lower cap. The Average Ramp Weight and Average Flight Time have been replaced by a Total Flight limitation.