ALERT SERVICE BULLETIN

MBB BK117 C-2

MBB BK117 C-2-71A-003

PAGE 1 of 13

2006-10-24

REVISION 03, 2007-12-11

Power Plant – Power Control – Accomplishment of ”MAX N1 CHECK”

1. Planning Information

A. Effectivity

(1) Helicopters affected: All MBB BK117 C-2 equipped with Turbomeca Arriel 1E2

engines.

(2) Components affected: FCU without modification TU 358 by Turbomeca *).

(3) Spare Parts affected: FCU without modification TU 358 by Turbomeca *).

NOTE *) Modification of a FCU i.a.w. TU 358 is either retrofitted with Turbomeca

Service Bulletin No. 292 73 0358 or installed by Turbomeca before new

supply of a FCU. In both cases the accomplishment of TU 358 is 

confirmed by an entry in the log card of the FCU by Turbomeca.

B. Concurrent Requirements

Immediately after receipt of this Alert Service Bulletins the pilots must be informed of its

contents.

C. Reason

EUROCOPTER performs the ”MAX N1 CHECK” i.a.w. MSM 05-60-00, 6-9 prior to delivery

on each helicopter at an altitude (PA) of about 10000 ft. This test was successful for every

delivered helicopter.

During supplementary testings “MAX N1 CHECK” at EUROCOPTER at maximum

certification altitude a few MBB BK117 C-2 helicopters could not reach the specified N1

power threshold value.

After a first analysis, the suspected root cause is an engine acceleration limitation due to a

delivered fuel flow lower than the engine fuel flow demand to achieve the OEI rating at high

altitude. The fuel flow is limited by the FCU acceleration law in those cases.

Therefore it is anticipated, that this limitation could potentially occur at altitudes higher than

10000 ft depending on the engine and FCU characteristics.

As a conservative measure TURBOMECA and EUROCOPTER have decided that take-off,

landing and HIGE/HOGE higher than 10000 ft or level flight above 13000 ft requires a

dedicated mandatory check.

If your operation requires to perform flights in altitudes higher than the above mentioned

values, a ”MAX N1 CHECK” according to this Alert Service Bulletin has to be performed.
ALERT SERVICE BULLETIN

MBB BK117 C-2

MBB BK117 C-2-71A-003

PAGE 2 of 13 REVISION 03, 2007-12-11

2006-10-24

D. Description

Mandatory check of engine power rating for take-off, landing and HIGE/HOGE in pressure

altitude higher than 10000 ft or level flight above 13000 ft, and if necessary, limitation of the

maximum permissible flight altitude.

E. Compliance

EFFECTIVITY FCUs without modification TU 358 by Turbomeca.

(1) If take-off, landing and hovering procedures in or out of ground effect are accomplished

up to pressure altitudes of a maximum of 10000 ft and mission flights are accomplished

in pressure altitudes up to a maximum of 13000 ft, proceed i.a.w. section 3.B of this Alert

Service Bulletin.

(2) If take-off, landing and hovering procedures in or out of ground effect in pressure

altitudes higher than 10000 ft or mission flights in pressure altitudes which are higher

than 13000 ft are to be accomplished, a maintenance check flight i.a.w. section 3.A of

this Alert Service Bulletin must be performed once in order to verify the availability of

the OEI rating of the engines.

This maintenance check flight must be performed before the next mission flight.

(3) If the engine and/or the FCU, and/or engine module 2 and/or the engine module 3 is

replaced, the accomplishment of this Alert Service Bulletin must be repeated i.a.w.

section 3.A of this Alert Service Bulletin.

(4) Accomplishment of this Alert Service Bulletin must be repeated with the Periodical

Inspection (600 Fh).

EFFECTIVITY Helicopters on which Alert Service Bulletin MBB-BK117 C-2-71A-003 has

already been accomplished before Revision 03 and then modification 

TU 358 was installed.

(5) After accomplishment of TU 358 on the FCUs of the two engines, the helicopters are

no longer affected by Alert Service Bulletin MBB BK117 C-2-71A-003 and the measures

i.a.w. Section 3.F, 3.G and 3.H are to be accomplished.

F. Approval

The technical content of this document is approved under the authority of

DOA No. EASA.21J.034

G. Manpower

Not applicable.

H. Weight and Balance

Not applicable.
ALERT SERVICE BULLETIN

MBB BK117 C-2

MBB BK117 C-2-71A-003

PAGE 3 of 13

2006-10-24

REVISION 03, 2007-12-11

I. Electrical Load Data

Not applicable.

J. Software Accomplishment Summary

Not applicable.

K. References

MSM MBB BK117 C-2.

L. Other Publications affected

The changes to FLM MBB BK117 C-2 and MSM MBB BK117 C-2 which are required as a

result of this Alert Service Bulletin will be incorporated with one of the next revisions.

M. Interchangeability of Parts

Not applicable.

2. Material Information

A. Material – Price and Availability

Not applicable.

B. Support Information

Not applicable.

C. Material Necessary for Each Helicopter

Not applicable.

D. Material Necessary for Each Spare

Not applicable.

E. Reidentified Parts

Not applicable.

F. Special Tooling

Not applicable.
ALERT SERVICE BULLETIN

MBB BK117 C-2

MBB BK117 C-2-71A-003

PAGE 4 of 13 REVISION 03, 2007-12-11

2006-10-24

3. Accomplishment Instructions

A. Accomplishment of ”MAX N1 CHECK”:

EFFECTIVITY For take-off, landing and hovering procedures in or out of ground

effect and for mission flights in pressure altitudes up to a maximum

of 18000 ft.

NOTE Expect Climbing during collective pull.

NOTE The ”MAX N1 CHECK” is to be performed as a maintenance check flight

by a qualified pilot. A second crew member is recommended to support

parameter observation.

NOTE If the ”MAX N1 CHECK” is not successful in the chosen pressure altitude,

accomplish the ”MAX N1 CHECK” in the next lower pressure altitude.

EFFECTIVITY Only after engine and/or FCU and/or module 2 and/or module 3

replacement.

(1) Preparation (shortened VARTOMS adjustment):

NOTE The shortened VARTOMS adjustment has to be accomplished in

hover flight and density altitude lower than 3600 ft.

(a) Switch VARTOMS to NORM mode. Check NRo/N2 to be 100%+2%.

(b) Switch VARTOMS to MAN mode and decrease NRo/N2 to MIN. Check torque

difference TRQ1–TRQ2>10% and check NRo>95%.

(c) Increase NRo/N2 to MAX. Check torque difference TRQ2–TRQ1>10% and check

NRo<104%.

EFFECTIVITY All.

(1) Accomplish ”MAX N1 CHECK”:

(a) Set bleed air consumers to off.

(b) Reduce electrical loads as much as possible, but generators remain on.

(c) Establish level flight (approx. 65 KIAS) at AEO condition in 17500 ft PA.

(d) Switch VARTOMS to MAN mode and trim to NRo=102 %.
ALERT SERVICE BULLETIN

MBB BK117 C-2

MBB BK117 C-2-71A-003

PAGE 5 of 13

2006-10-24

REVISION 03, 2007-12-11

(e) Reduce engine not to be tested to IDLE condition and trim rotor speed to

NRo=101 %.

CAUTION DO NOT STAY WITHIN THE 2.5 MIN OEI RATING FOR MORE THAN

10 SEC. AND DO NOT UNDERSHOOT ROTOR RPM.

IF MORE THAN 10 SECONDS OF 2.5 MIN OEI RATING HAS BEEN

USED, RECORD THIS EVENT I.A.W. THE FLIGHT MANUAL.

CAUTION IF THE TEST IS REPEATED ON THE SAME ENGINE, A “COOL

DOWN TIME” OF AT LEAST 1 MINUTE AT OEI MCP LEVEL OR

BELOW SHOULD BE OBSERVED BEFORE TO PERFORM A

FURTHER “MAX N1 CHECK” ATTEMPT.

(f) Maintain airspeed (approx. 65 KIAS) and pull collective pitch lever up to power

setting FLI=12 (2.5 min OEI-limit) and verify N1 increase up to value of ”Maximum

N1 Datum Table” of MSM 05-60-00, 6-9 (Fig. 606) and check rotor RPM.

(g) When N1 limit is reached, the rotor speed must not drop below 98 %.

(h) Note the value of N1 of the respective engine if the N1 limit is not reached.

(2) If the OEI rating is reached, proceed i.a.w. section 3.C of this Alert Service Bulletin.

(3) If the OEI rating is not reached, take-off, landing and hovering procedures in or out of

ground effect up to a pressure altitude of a maximum of 10000 ft and mission flights in

pressure altitudes up to a maximum of 13000 ft may be accomplished, proceed i.a.w.

section 3.B of this Alert Service Bulletin or with the next possible “MAX N1 CHECK” in

a lower altitude.

EFFECTIVITY For take-off, landing and hovering procedures in or out of ground

effect and for mission flights in pressure altitudes up to a maximum

of 16000 ft.

NOTE Expect Climbing during collective pull.

NOTE The ”MAX N1 CHECK” is to be performed as a maintenance check flight

by a qualified pilot. A second crew member is recommended to support

parameter observation.

NOTE If the ”MAX N1 CHECK” is not successful in the chosen pressure altitude,

accomplish the ”MAX N1 CHECK” in the next lower pressure altitude.

(1) Accomplish ”MAX N1 CHECK”:

(a) Set bleed air consumers to off.

(b) Reduce electrical loads as much as possible, but generators remain on.
ALERT SERVICE BULLETIN

MBB BK117 C-2

MBB BK117 C-2-71A-003

PAGE 6 of 13 REVISION 03, 2007-12-11

2006-10-24

(c) Establish level flight (approx. 65 KIAS) at AEO condition in 15500 ft PA.

(d) Switch VARTOMS to MAN mode and trim to NRo=102 %.

(e) Reduce engine not to be tested to IDLE condition and trim rotor speed to

NRo=101 %.

CAUTION DO NOT STAY WITHIN THE 2.5 MIN OEI RATING FOR MORE THAN

10 SEC. AND DO NOT UNDERSHOOT ROTOR RPM.

IF MORE THAN 10 SECONDS OF 2.5 MIN OEI RATING HAS BEEN

USED, RECORD THIS EVENT I.A.W. THE FLIGHT MANUAL.

CAUTION IF THE TEST IS REPEATED ON THE SAME ENGINE, A “COOL

DOWN TIME” OF AT LEAST 1 MINUTE AT OEI MCP LEVEL OR

BELOW SHOULD BE OBSERVED BEFORE TO PERFORM A

FURTHER “MAX N1 CHECK” ATTEMPT.

(f) Maintain airspeed (approx. 65 KIAS) and pull collective pitch lever up to power

setting FLI=12 (2.5 min OEI-limit) and verify N1 increase up to value of ”Maximum

N1 Datum Table” of MSM 05-60-00, 6-9 (Fig. 606) and check rotor RPM.

(g) When N1 limit is reached, the rotor speed must not drop below 98 %.

(h) Note the value of N1 of the respective engine if the N1 limit is not reached.

(2) If the OEI rating is reached, take-off, landing and hovering procedures in or out of

ground effect and mission flights up to pressure altitudes of a maximum of 16000 ft may

be accomplished, proceed i.a.w. section 3.B of this Alert Service Bulletin.

(3) If the OEI rating is not reached, take-off, landing and hovering procedures in or out of

ground effect up to a pressure altitude of a maximum of 10000 ft and mission flights in

pressure altitudes up to a maximum of 13000 ft may be accomplished, proceed i.a.w.

section 3.B of this Alert Service Bulletin or with the next possible “MAX N1 CHECK” in

a lower altitude.
ALERT SERVICE BULLETIN

MBB BK117 C-2

MBB BK117 C-2-71A-003

PAGE 7 of 13

2006-10-24

REVISION 03, 2007-12-11

EFFECTIVITY For take-off, landing and hovering procedures in or out of ground

effect and for mission flights in pressure altitudes up to a maximum

of 13000 ft.

NOTE Expect Climbing during collective pull.

NOTE The ”MAX N1 CHECK” is to be performed as a maintenance check flight

by a qualified pilot. A second crew member is recommended to support

parameter observation.

(1) Accomplish ”MAX N1 CHECK”:

(a) Set bleed air consumers to off.

(b) Reduce electrical loads as much as possible, but generators remain on.

(c) Establish level flight (approx. 65 KIAS) at AEO condition in 12500 ft PA.

(d) Switch VARTOMS to MAN mode and trim to NRo=102 %.

(e) Reduce engine not to be tested to IDLE condition and trim rotor speed to

NRo=101 %.

CAUTION DO NOT STAY WITHIN THE 2.5 MIN OEI RATING FOR MORE THAN

10 SEC. AND DO NOT UNDERSHOOT ROTOR RPM.

IF MORE THAN 10 SECONDS OF 2.5 MIN OEI RATING HAS BEEN

USED, RECORD THIS EVENT I.A.W. THE FLIGHT MANUAL.

CAUTION IF THE TEST IS REPEATED ON THE SAME ENGINE, A “COOL

DOWN TIME” OF AT LEAST 1 MINUTE AT OEI MCP LEVEL OR

BELOW SHOULD BE OBSERVED BEFORE TO PERFORM A

FURTHER “MAX N1 CHECK” ATTEMPT.

(f) Maintain airspeed (approx. 65 KIAS) and pull collective pitch lever up to power

setting FLI=12 (2.5 min OEI-limit) and verify N1 increase up to value of ”Maximum

N1 Datum Table” of MSM 05-60-00, 6-9 (Fig. 606) and check rotor RPM.

(g) When N1 limit is reached, the rotor speed must not drop below 98 %.

(h) Note the value of N1 of the respective engine if the N1 limit is not reached.

(2) If the OEI rating is reached, take-off, landing and hovering procedures in or out of

ground effect and mission flights up to pressure altitudes of a maximum of 13000 ft may

be accomplished, proceed i.a.w. section 3.B of this Alert Service Bulletin.

(3) If the OEI rating is not reached, take-off, landing and hovering procedures in or out of

ground effect up to a pressure altitude of a maximum of 10000 ft and mission flights in

pressure altitudes up to a maximum of 13000 ft may be accomplished, proceed i.a.w.

section 3.B of this Alert Service Bulletin.
ALERT SERVICE BULLETIN

MBB BK117 C-2

MBB BK117 C-2-71A-003

PAGE 8 of 13 REVISION 03, 2007-12-11

2006-10-24

B. Affixing of placard:

(1) Copy page 9 of this Alert Service Bulletin.

(2) Choose placard (1, Figure 1) corresponding to the maximum permissible pressure

altitude and cut out.

(3) Using a transparent adhesive tape, affix placard (1, Figure 1) to a place in the cockpit

which can be easily seen by the pilot.

C. Copy the flight manual pages attached to this Alert Service Bulletin, cut out and insert behind

the affected FLM pages.

D. After accomplishment of the “MAX N1 CHECK”, fill out copy of reply form sheet from page 13

and send to ECD and Turbomeca.

E. Confirm accomplishment of this Alert Service Bulletin by an entry in the historical record of

the helicopter.

EFFECTIVITY After accomplishment of modification TU 358 on both engines.

F. If affixed, remove placard (1, Figure 1) from helicopter.

G. Remove the flight manual pages enclosed with this Alert Service Bulletin from FLM.

H. Removal of the possibly affixed placard and removal of the flight manual pages must be

confirmed by an entry in the helicopter‘s historical record.

4. Appendix

– Flight manual pages

– Alert Service Letter of the Turbomeca company
ALERT SERVICE BULLETIN

MBB BK117 C-2

MBB BK117 C-2-71A-003

PAGE 9 of 13

2006-10-24

REVISION 03, 2007-12-11

Placard for Maximum Pressure Altitude

Figure 1

1 Placard

Choose placard corresponding to the maximum permissible flight altitude and cut out.

Using a transparent adhesive tape, affix placard to a place in the cockpit which can be

easily seen by the pilot.

Maximum altitude for

take-off, landing and

HOGE is 

10000 ft PA

Maximum operating

altitude is 

13000 ft PA

ASB-MBB BK117 C-2-71A-003

Maximum operating

altitude is 

16000 ft PA

ASB-MBB BK117 C-2-71A-003

1

1

Maximum operating

altitude is 

13000 ft PA

1

ASB-MBB BK117 C-2-71A-003
ALERT SERVICE BULLETIN

MBB BK117 C-2

MBB BK117 C-2-71A-003

PAGE 10 of 13 REVISION 03, 2007-12-11

2006-10-24
ALERT SERVICE BULLETIN

MBB BK117 C-2

MBB BK117 C-2-71A-003

PAGE 11 of 13

2006-10-24

REVISION 03, 2007-12-11
ALERT SERVICE BULLETIN

MBB BK117 C-2

MBB BK117 C-2-71A-003

PAGE 12 of 13 REVISION 03, 2007-12-11

2006-10-24
ALERT SERVICE BULLETIN

MBB BK117 C-2

MBB BK117 C-2-71A-003

PAGE 13 of 13

2006-10-24

REVISION 03, 2007-12-11

Telefax

To

Eurocopter Deutschland GmbH

Customer Service

FAX 0049 906714111

Date:__________ Signature:___________________

Alert Service Bulletin MBB BK117 C-2-71A-003 ”MAX N1 CHECK” has

been accomplished.

Reply form sheet for accomplishment of the “MAX N1 CHECK”:

Please copy page! The original page remains in the ASB!

In order to clearly determine the reason why the OEI rating has not been reached

in higher Pressure Altitudes, it is necessary to report the data mentioned below to

ECD and Turbomeca.

In case of further problems contact ECD or Turbomeca field representative.

Helicopter S/N:

“MAX N1 CHECK” accomplished in

Pressure Altitude: ft, successful engine LH yes / no –– N1-Value

ft, successful engine RH yes / no –– N1-Value

ft, successful engine LH yes / no –– N1-Value

LH engine S/N:

RH engine S/N:

LH FCU S/N:

RH FCU S/N:

To

Turbomeca

Local TM Field Representative

ft, successful engine RH yes / no –– N1-Value

ft, successful engine LH yes / no –– N1-Value

ft, successful engine RH yes / no –– N1-Value

%

%

%

%

%

%

Alert letter

OPERATOR SUPPORT

40220 Tarnos – France

Tél. (33) (0) 5 59 74 40 00

Télex 570 042

Fax (33) (0) 5 59 64 74 98

Technical Support Department

Fax (33) (0) 5 59 74 45 34

JSV/BF/MD

Service Letter No. 2495/06/AR1E/29

Subject: ARRIEL 1 E2.

Engine power ratings availability at high altitude.

Bordes, October 23, 2006

SIEGE SOCIAL ET DIRECTION GENERALE : 64511 Bordes Cedex – France

Tél. (33) 5 59 12 50 00 – Télex 560 928 – Fax (33) 5 59 53 15 12

TURBOMECA - Brevets Szydlowski – Société Anonyme au capital de 38.553.056 Euros – Registre du Commerce et des Sociétés Pau B 338 481 955 1/2

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To the attention

of maintenance

personnel and

crews

Dear Madam, Sir,

The MBB BK117 C-2 (EC145) Master Servicing Manual (MSM) tasks 05-60-00 or MBB BK117

C-1 Maintenance Manual (MM), appendix E "MAX N1 check" aims to check the availability of the

ARRIEL 1 E2 engine OEI 2.5-min rating.

The OEI 2.5-min rating is designed to be used with one engine inoperative during take-off,

landing or hover in / out-off ground effect (HIGE / HOGE).

EUROCOPTER performs this “MAX N1 check” prior delivery on each helicopter at an altitude

(PA pressure altitude) of about 10.000 ft. This test was successful for every delivered helicopter.

During supplementary testing at EUROCOPTER at maximum certification altitude a few MBB

BK117 C-2 helicopters failed this test.

Therefore it is anticipated, that this behaviour could potentially occur at altitudes higher than

10.000 ft depending on the engine and FCU characteristics.

After a first analysis, the suspected root cause is an engine acceleration limitation due to a

delivered fuel flow lower than the engine fuel flow demand to achieve the OEI 2.5-min rating at

high altitude. The fuel flow is limited by the FCU acceleration law in this case.

As a conservative measure TURBOMECA and EUROCOPTER have decided that take-off,

landing and hover HIGE / HOGE higher than 10000 ft or level flight above 13000 ft require a

mandatory dedicated check.

Should you require to perform operations in altitudes higher than the above mentioned values, a

“MAX N1 check” according to ECD Alert Service Bulletin MBB BK117 C-2-71A-003 or MBB

BK117-60-121 has to be performed successfully prior to operate at the desired altitude.
Alert Letter No. 2495/06/AR1E/29

2/2

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If the "N1 max" check is not successful, please contact your local TURBOMECA field

representative and continue to operate according to the ECD Alert Service Bulletin.

TURBOMECA is putting the highest priority in order to define a corrective action, which will allow

recovering the initial whole flight envelope.

Pending the results of the further analyses in progress, we would like to highlight that the engine

or FCU exchange will not allow fixing the issue.

We will keep you informed of the results of the analyses, and appropriate corrective action.

Please do not hesitate to contact us if you require any other information.

J-S. VIGNES

Technical Support Department