Ref No.: AOT-CN235-57-0001 

Rev No.: 1 Rev Date: 14/03/2014

SERVICES DIRECTORATE

Po John Lennon s/n 

28906 Getafe, Madrid, SPAIN 

MTA.TechnicalService@military.airbus.com

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ATA Chapter: 57 

Subject: Inspection of Aileron Control Rod Fittings

Aircraft Type: CN-235 

Applicability: All CN-235 

Limited Distribution: N/A 

Referenced Documents: 

Ref.1: IPC 57-61-19-001-01-01 - Item 170 

Ref.2: IPC 57-61-19-001-01-01 - Item 180 

Ref.3: AMM 57-61-11 – Aileron Removal/Installation

1. REASON FOR REVISION 

Rev No.1: Correction of typing error in Annex 1- Paragraph 4.C. 

2. REASON 

2.1 FACTS

One CN-235 Operator recently reported cases of cracks on the control rod fittings (inboard and outboard) of the 

ailerons (RH & LH side) of two aircraft. These findings were detected during scheduled maintenance tasks. 

The cracks are located on the lugs of the control rod fittings (see Ref.1 and Ref.2). At the time of finding the two aircraft 

had accumulated between 16000 and 17000 Flight Hours (FH), around 6000 Flight Cycles (FC) and 20 years in service. 

2.2 CONSEQUENCES

If the failure of a control rod fitting (inboard or outboard) does not cause aileron jamming, the operation of the affected 

aileron can still be ensured with the other control rod. 

In case of jamming of the affected aileron, the UNTIE of FLT CONT DISC ROLL switch would allow the crew to control 

the other operative aileron. 

2.3 AIM

The aim of this AOT is to verify the integrity of the control rod fittings by means of a onetime Non-Destructive 

Inspection (NDT Inspection) of the ailerons control rod fitting lugs for cracks. 
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Subject: Inspection of Aileron Control Rod Fittings 

3. SHORT TERM ACTION 

3.1 PLANNING AND MANPOWER

3.1.1 ACCOMPLISHMENT TIMESCALE 

The inspection described in annex I has to be performed on all CN-235 aircraft with more than 10 years or 8000 FH 

since the first flight, whichever occurs first, at the next scheduled maintenance inspection. 

3.1.2 MANPOWER 

The estimated time to get access and perform the Inspection is 30 men hours per aircraft. 

3.2 DESCRIPTION

3.2.1 ACCESS 

Inspection must be performed with the aileron removed from the aircraft in accordance with Ref.3. 

3.2.2 INSPECTION REQUIREMENTS 

Refer to annex 1 for the complete instructions to accomplish the NDT inspection. 

3.2.3 FINDINGS 

In case of a cracked lug of the control rod fittings is identified, before next flight contact Airbus Military with a detailed 

damage report to get further instructions. 

3.3 SPARES AND TOOLING

Refer to annex 1 for inspection equipment. 

4. FURTHER INFORMATION 

4.1 FOLLOW-UP PLAN

Further actions may be considered based upon results of the ongoing investigations. 

4.2 IMPACTED DOCUMENTATION

Not applicable. 
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ATA Chapter: 57 

Subject: Inspection of Aileron Control Rod Fittings 

5. REPORTING 

Questions about this AOT and inspection results with or without findings are to be sent to Airbus Military Technical 

Assistance Center (AMTAC): 

Telephone: (+34) 91 600 79 99 

E-mail: MTA.TechnicalService@military.airbus.com 

Released by

Yannick Ville 

© EADS CASA.2013. All rights reserved. Confidential and proprietary document. 

This document and all information contained herein is the sole property of EADS CASA. 

No intellectual property rights are granted by the delivery of this document or the disclosure of its content. This document shall not be reproduced or disclosed to a third party without the 

express written consent of EADS CASA. 

This document and its content shall not be used for any purpose other than that for which it is supplied.

©EADS CASA 2013 All right reserved 

 
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Subject: Inspection of Aileron Control Rod Fittings 

ANNEX 1 – NDT INSPECTION 

1 COMPONENT OR AREA TO BE INSPECTED (refer to Figure 1) 

 

A. The hinge fittings of the aileron attachment to the outer wing at stations Y=8110, Y=9910 and Y=11750 and the actuator 

attachment fittings at Y=8110 and Y=9910. LH and RH. 

B. At station Y=8110 the wingbox side hinge fitting, the aileron side hinge fitting and the actuator fittings are to be 

inspected. Inspection areas are both surfaces of each lug around the lug bushings. 

C. At station Y=9910 the intermediate linkage part, the aileron side hinge fitting and the actuator fittings will be inspected. 

Inspection areas are both surfaces of each lug around the bushings and the upper and lower fillet radii of the intermediate 

linkage part. 

D. At station Y=11750 the intermediate linkage part and the aileron side hinge fitting will be inspected. Inspection areas are 

both surfaces of each lug around the bushings and the upper and lower fillet radii of the intermediate linkage part. 

2 DESCRIPTIONOF POSSIBLE DAMAGE (refer to Figure 2)

A. Fatigue cracks emanating from the inner diameter of the lug extending radially. Cracks will be detectable when equal or 

greater than 2 mm (0.079 in) from the bushing edge.

B. Fatigue cracks equal or greater than 2 mm (0.079 in.) starting at the edge of the fillet radius and propagating along the 

radius and across the section of the fitting base. 

3 EQUIPMENT AND MATERIALS 

A. Any equivalent eddy current equipment with scope display/probe combination which satisfies the requirements of this 

procedure may be used. 

B. The equipment used in the development of this procedure was as follows: 

 1. Instrument: NORTEC 2000 from OLYMPUS. 

 2. Probes: Absolute shielded probe PAB-90C401 (cranked probe), 

 1 MHz with probe tip diameter 0,125 in., microdot connector from EC NDT 

 Absolute shielded extra-flat probe MP.060-60BL, 50-500kHz from Olympus 

 NOTE: Flat probe not needed if aileron is removed. 

 3. Cable: EC-N2K-TL-6 (Lemo 0 triaxial to Lemo 16p) from EC NDT 

 4. Calibration Standard: 2-164-551, NFe from Institut Dr. Foerster (shown in Figure 3) 
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4 PREPARATION FOR INSPECTION 

 WARNING: MAKE SURE THAT ALL SAFETY PROCEDURES ARE FOLLOWED TO PREVENT INJURY TO PERSON 

 OR DAMAGE TO THE AIRCRAFT. ENSURE THAT NECESSARY WARNING NOTICES ARE IN POSITION BEFORE 

 YOU START THE TASK. 

A. It might be necessary to remove the aileron completely to get proper access to the inspection areas. 

B. Ensure that there is no sealant on the inspection area. 

C. Ensure that paint coating thickness does not excess 350 μm. 

 (1) If the paint thickness is greater than 350 μm, the inspection cannot be done. The paint must be stripped or 

 reduced in thickness to less than 350μm. 

 (2) If the paint thickness is less than 350 μm, a plastic foils corresponding to the paint thickness (±30 μm), must be 

 placed on the surface of the calibration standard during calibration steps. 

D. Make sure that the surface of the inspection area is clean and smooth. 

 NOTE: The area to be inspected (refer to Figure 1) has to be visually checked for discontinuities such as bulging, 

 dents, peeled paint, visible corrosion or any other condition that may affect accuracy of the eddy current 

 inspection. 

5 INSTRUMENT CALIBRATION (refer to Figure 4) 

A. Set the instrument test parameters as indicated below: 

 Frequency: 1 MHz/ 500kHz, depending on the probe. 

 H-Pos: 70 

 V-Pos: 20 

 Probe drive: Medium 

B. Use calibration standard 2.164-551 to calibrate the instrument in accordance with the manufacturer’s instructions. 

C. Position the probe on a slot-free area and press Null to adjust the zero of the instrument. 

D. Alternatively place and move the probe away from the calibration standard while adjusting phase angle to get a 

horizontal lift-off response equivalent to that shown in Figure 4. 

E. Move the probe across the 0,5 mm slot in the calibration standard and adjust the instrument sensitivity (gain) to get a 

signal amplitude of 50% FSH and similar shape as that shown in Figure 4. 

F. Move the probe across the 0,2 mm slot in the calibration standard and confirm that the indication on the screen is greater 

than 10% of the screen height. 
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Subject: Inspection of Aileron Control Rod Fittings 

6 INSPECTION PROCEDURE (refer to Figure 5) 

A. Place the selected probe on the fitting surface (compensation point) and press Null to adjust the zero of the instrument in 

the screen. 

 NOTE: One compensation point will be selected for each fitting and for each different area: for the lug it will be 

 close the bushing and for the fillet radius and cross section will be the fitting surface. 

B. Alternatively place and move the probe away from the compensation point while adjusting the phase angle to get a 

horizontal lift-off response. Do not modify any other of the parameters got during calibration. 

C. Slide the probe on both surfaces of each lug as close as possible to the fitting bushing. 

D. Slide the probe across the fillet radius using the scanning movements indicated in Figure 5. 

E. Inspect the fillet radius section by sliding the probe as close as possible to the fitting base edge. 

E. Any screen indication similar to that shown in Figure 4 greater than 10% FSH not caused by the bushing edge effect or 

any other geometrical effect shall be considered as a crack. 

F. Record position of any crack indication. 

G. Evaluate the length of any crack scanning from the point of maximum amplitude towards its side in parallel scanning 

paths with 1 mm index up to the point where the amplitude reduces to 10% FSH. 

7 ACCEPTANCE CRITERIA 

All indication which cause screen deflection equal or greater than 10% FSH above the zero point similar to that shown in 

Figure 4 not caused by edge effect, the effect of the bushing or any other geometrical effect shall be considered as a crack 

and must be recorded 

8 FINAL NDT REQUIREMENTS 

None. 
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