October 24, 2006

Rev. 4, December 11, 2007

ASB-MBB-BK117-60-121

Page 1 of 17

1. PLANNING

1.A. Effectivity

1.A.1. Helicopters affected: All MBB-BK117 C-1 with Turbomeca engine Arriel 1E2.

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

1.A.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.

1.B. Reason

EUROCOPTER performed the ”MAX N1 Check” i.a.w. MM, Appendix E 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. As the same engine is used on the helicopter

MBB BK117 C-1, this problem may also occur on these helicopter models.

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.

Date: October 24, 2006

Rev. 4, December 11, 2007

ALERT SERVICE BULLETIN

MBB-BK117

No. ASB-MBB-BK117-60-121

Subject: Power Plant – Power Control – Accomplishment of “MAX N1 CHECK”
October 24, 2006

Rev. 4, December 11, 2007

ASB-MBB-BK117-60-121

Page 2 of 17

1.C. 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.

1.D. Compliance

EFFECTIVITY FCUs without modification TU 358 by Turbomeca.

1.D.1. If starting, 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 2.B.2 of this Alert Service Bulletin.

1.D.2. If starting, 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 2.B.1

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.

1.D.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 2.B.1 of this Alert Service Bulletin.

1.D.4. Accomplishment of this Alert Service Bulletin must be repeated with the Periodical

Inspection (600 Fh).

EFFECTIVITY Helicopters on which Alert Service Bulletin MBB-BK117-60-121 has

already been accomplished before Revision 04 and then modification 

TU 358 was installed.

1.D.5. After accomplishment of TU 358 on the FCUs of the two engines, the helicopters are

no longer affected by Alert Service Bulletin MBB BK117-60-121 and the measures

i.a.w. Section 2.B.6, 2.B.7 and 2.B.8 are to be accomplished.

1.E. Approval

The technical content of this document is approved under the authority of DOA No.

EASA.21J.034.

1.F. Manpower Requirement

(not applicable)

1.G. Material, Cost and Availability

(not applicable)

1.H. Special Tools

(not applicable)
October 24, 2006

Rev. 4, December 11, 2007

ASB-MBB-BK117-60-121

Page 3 of 17

1.I. Mass and Moment

(not applicable)

1.J. Reference

– FLM MBB-BK 117 C-1

– FLM MBB-BK 117 C-1C

1.K. Other Publications affected

– FLM MBB-BK 117 C-1 (see appendix)

– FLM MBB-BK 117 C-1C (effective for MBB-BK117 C-1C, S/N 7511, distributed

separately) .

– MM MBB BK 117 C

1.L. Electrical Load Data

(not applicable)

2. ACCOMPLISHMENT INSTRUCTIONS

2.A. Inspections Required

(not applicable)

2.B. Work Procedure

2.B.1. Accomplishment of ”MAX N1 CHECK”:

EFFECTIVITY For starting, 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.

2.B.1.1. Accomplish ”MAX N1 CHECK”:

(a) Set bleed air consumers to off.

(b) Reduce electrical loads as much as possible, but generators remain on.
October 24, 2006

Rev. 4, December 11, 2007

ASB-MBB-BK117-60-121

Page 4 of 17

(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%.

(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 nN1=1,3 % (2,5 min OEI-limit) and verify N1 increase up to value of ”N1

TACHO CHECK TABLE” of FLM MBB BK117 C-1 or FLM MBB BK117 C-1C 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.B.1.2. If the OEI rating is reached, proceed i.a.w. section 2.B.3 of this Alert Service

Bulletin.

2.B.1.3. If the OEI rating is not reached, starting, 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 2.B.2 of this Alert Service Bulletin or with the next possible

“MAX N1 CHECK” in a lower altitude.

EFFECTIVITY For starting, 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.

2.B.1.4. Accomplish ”MAX N1 CHECK”:

(a) Set bleed air consumers to off.
October 24, 2006

Rev. 4, December 11, 2007

ASB-MBB-BK117-60-121

Page 5 of 17

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

(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 nN1=1,3 % (2,5 min OEI-limit) and verify N1 increase up to value of ”N1

TACHO CHECK TABLE” of FLM MBB BK117 C-1 or FLM MBB BK117 C-1C, 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.B.1.5. If the OEI rating is reached, starting, 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 2.B.2 of this Alert Service Bulletin.

2.B.1.6. If the OEI rating is not reached, starting, 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 2.B.2 of this Alert Service Bulletin or with the next possible

“MAX N1 CHECK” in a lower altitude.
October 24, 2006

Rev. 4, December 11, 2007

ASB-MBB-BK117-60-121

Page 6 of 17

EFFECTIVITY For starting, 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.

2.B.1.7. 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 nN1=1,3 % (2,5 min OEI-limit) and verify N1 increase up to value of ”N1

TACHO CHECK TABLE” of FLM MBB BK117 C-1 or FLM MBB BK117 C-1C, 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.B.1.8. If the OEI rating is reached, starting, 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 2.B.2 of this Alert Service Bulletin.

2.B.1.9. If the OEI rating is not reached, starting, landing and hovering procedures in or out

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

flights in pressure altitudes up to a maximum of 13000 ft may be accomplished.

Proceed i.a.w. section 2.B.2 of this Alert Service Bulletin.
October 24, 2006

Rev. 4, December 11, 2007

ASB-MBB-BK117-60-121

Page 7 of 17

2.B.2. Affixing of placard:

2.B.2.1. Copy page 8 of this Alert Service Bulletin.

2.B.2.2. Choose placard (1, Figure 1) corresponding to the maximum permissible Pressure

Altitude and cut out.

2.B.2.3. Using a transparent adhesive tape, affix placard (1, Figure 1) to a place in the

cockpit which can easily seen by the pilot.

2.B.3. Copy the flight manual pages attached to this Alert Service Bulletin, cut out and

insert behind the affected FLM pages.

2.B.4. After accomplishment of the “MAX N1 CHECK”, fill out copy of reply form sheet from

page 17 and send to ECD and Turbomeca.

2.B.5. 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.

2.B.6. If affixed, remove placard (1, Figure 1) from helicopter.

2.B.7. Remove the flight manual pages enclosed with this Alert Service Bulletin from FLM.

2.B.8. 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.

2.C. Conclusions

(not applicable)

3. MATERIAL INFORMATION

(not applicable)
October 24, 2006

Rev. 4, December 11, 2007

ASB-MBB-BK117-60-121

Page 8 of 17

Placard for Maximum Pressure Altitude

Figure 1

Maximum altitude for

take-off, landing and

HOGE is 

10000 ft PA

Maximum operating

altitude is 

13000 ft PA

Maximum operating

altitude is 

16000 ft PA

Maximum operating

altitude is 

13000 ft PA

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.

ASB-MBB BK117-60-121

ASB-MBB BK117-60-121

ASB-MBB BK117-60-121

1

1

1
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Telefax

To

Eurocopter Deutschland GmbH

Customer Service

FAX 0049 906714111

Date:__________ Signature:___________________

Alert Service Bulletin MBB BK117-60-121 ”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