Federal Department of the Environment, Transport, Energy and 

Communications DETEC

Federal Office of Civil Aviation FOCA

Safety Division - Aircraft

Lufttüchtigkeitsanweisung (LTA)

Consigne de Navigabilité (CN)

Direttive sulla Navigabilità (DN)

Airworthiness Directive (AD)

FOCA AD

HB-2014-001

Inkraftsetzung

Mise en vigueur

Entrata in vigore

Effective Date

08 August 2014 Pilatus – PC-7

FOCA TC/TCDS No: F 56-20

1/2

Rechtsgrundlage: Art. 26, 51 und 51A (Verordnung über die Lufttüchtigkeit von Luftfahrzeugen: SR 748.215.1)

Base juridique: Art. 26, 51 et 51A (Ordonnance sur la navigabilité des aéronefs: SR 748.215.1)

Base giuridica: Art. 26, 51 e 51A (Ordinanza concernente la navigabilità degli aeromobili: SR 748.215.1)

Legal base: Art. 26, 51 and 51A (Ordinance on the airworthiness of aircraft: SR 748.215.1)

Issue Date: 25 July 2014

ATA Chapter: ATA 51 – Standard Practices and Structures

Subject: Standard Practices and Structures – Aircraft Structure –

Identification of Material Specification, Inspection

Supersedure / Revised

AD(s):

Not applicable

Type Certificate 

Holder’s Name:

Pilatus Aircraft Ltd.

Manufacturer(s): Pilatus Aircraft Ltd.

Applicability: Model PC-7 aircraft, Manufacturer Serial Numbers (MSN) 101 through 

MSN 618.

Reason: This Airworthiness Directive (AD) is prompted due to the possibility of 

cracks in some critical parts. It is possible that stress corrosion cracks 

may occur on various parts of the aircraft structure initially made of aluminium alloy AA2024-T351 which is susceptible to Stress Corrosion 

Cracking (SCC). Later in production, the material specification was 

changed to aluminium alloy AA2124-T851 to decrease the risk of stress 

corrosion. The Part Number (P/N) of the affected structural parts are not 

always changed when the new material was introduced.

Such a condition, if left uncorrected, could lead to failure of critical parts 

on the aircraft structure and will prejudice the structural integrity of the 

aircraft.

In order to correct and control the situation, this AD requires a one-time 

check to identify the material specification and inspect the affected areas 

of the airframe that are made of aluminium alloy AA2024-T351. Any structural parts of the aircraft structure found to be cracked must be reported to 

Pilatus prior to further flight.

Required Action(s) 

and Compliance 

Time(s):

Required as indicated below, unless already accomplished, within the next 

365 days after the effective date of this AD:

(1) Perform a one time conductivity test of items 6 thru 9 and 11 thru 13 

(both on aircraft and those held in stores) as listed in paragraph (§). 

1.A.(2) of PILATUS PC-7 Service Bulletin No. 51-001, to check the 

material of the parts.
Lufttüchtigkeitsanweisung (LTA)

Consigne de Navigabilité (CN)

Direttive sulla Navigabilità (DN)

Airworthiness Directive (AD)

FOCA AD

HB-2014-001

2/2

Rechtsgrundlage: Art. 26, 51 und 51A (Verordnung über die Lufttüchtigkeit von Luftfahrzeugen: SR 748.215.1)

Base juridique: Art. 26, 51 et 51A (Ordonnance sur la navigabilité des aéronefs: SR 748.215.1)

Base giuridica: Art. 26, 51 e 51A (Ordinanza concernente la navigabilità degli aeromobili: SR 748.215.1)

Legal base: Art. 26, 51 and 51A (Ordinance on the airworthiness of aircraft: SR 748.215.1)

(2) If the parts are made of aluminium alloy AA2124-T851, make an entry 

in the aircraft logbook as required by § 3.D.(3) of PILATUS PC-7 Service Bulletin No. 51-001.

(3) Because it is difficult to inspect for cracks on the elevator center control-rods (Item 3 as listed in § 1.A.(2) of PILATUS PC-7 Service Bulletin No. 51-001), these type of control rods will be replaced.

(4) Parts (Items 1, 2, 4, 5 and 10 as listed in § 1.A.(2) of PILATUS PC-7 

Service Bulletin No. 51-001) are made of aluminium alloy AA2024-

T351. Therefore:

• Do a one time inspection for cracks of Items 1, 2, 4 and 10

• Replace Item 5

(5) If the conductivity test shows the parts are made of aluminium alloy 

AA2024-T351:

a) For Items 7 thru 9 and 11 thru 13 as listed in § 1.A.(2) of PILATUS PC-7 Service Bulletin No. 51-001, do a one time inspection for cracks. If cracks are found, contact Pilatus.

NOTE: Repetitive mandatory inspections will be added to 

Chapter 5 of the Aircraft Maintenance Manual (AMM). The inspections will give instructions on how to examine the parts for 

cracks. The inspections will only be applicable to parts made 

from AA2024-T351.

b) For Item 6 as listed in § 1.A.(2) of PILATUS PC-7 Service Bulletin No. 51-001, replace the part with a part made of aluminium alloy AA2124-T851.

Ref. Publication(s): PILATUS PC-7 Service Bulletin No. 51-001, initial issue.

The use of later approved revisions of this document is acceptable for 

compliance with the requirements of this AD.

For further information 

contact:

The applicable manufacturer’s documentation may be obtained directly 

from:

PILATUS AIRCRAFT LTD.

Customer Technical Support (MCC)

P.O. Box 992

CH-6371 Stans, Switzerland

Tel.: +41 (0)41 619 67 74 Fax: +41 (0)41 619 67 73

E-mail: Techsupport@pilatus-aircraft.com

For further information contact:

FEDERAL OFFICE OF CIVIL AVIATION (FOCA)

Design and Production (STEH)

CH-3003 Bern, Switzerland

Fax: +41 (0) 31 322 59 18

E-mail: airdir@bazl.admin.ch