Docket No: F AA-20 14-0493 

Directorate ID: 20 13-SW-0 19-AD 

Disposition Comments 

Originating Office Tracking No.: SPOl 703BO-R 

Next Step: [?$) FRA OS PRM 

D These comments are in 

response to an SN PRM 

D No Comments/Only Supportive Comments Received - If this box is checked, no signatures are 

required. 

No Has the referenced service information been revised since the NPRM was issued? If yes, 

list latest revision and attach a copy. Note that changes beyond the scope of the previously 

published NPRM11·il/ require a new notice. Contact/he Directorate.focal point for guidance. 

Instructions: Summarize all comments by issue (not by commenter) and provide your recommended resolution of 

each issue. All comments relating to the same issue should be discussed together. Do not list all of the issues 

from one commenter together. If changes to the AD are required based on the comments received, explain why and 

describe in detail what change(s) you recommend. Reference F AA-1 R-M-8040. 1 C Chapter 9. 

ISSUE 1: Select one qf the following: other 

If other. explain: Clarification to the Discussion 

Commenter(s): Sikorsky 

What change to the AD action is requested? Revise the wording in the Discussion paragraph. 

Why is the change requested or how is it justified? To provide a more descriptive narrative. 

Do we agree? Partially Agree 

If YES, we agree because Make the following changes to the AD: 

If PARTIALLY AGREE, we agree with some of the editorial changes because it provides 

clarification on function of the system We disagree with some of the editorial changes because it 

provides details not needed. Make the following changes to the AD: 

Discussion 

We propose to adopt a new AD for Sikorsky Model S-92A heli copters. This proposed AD 

would require. depending on the helicopter's serial number, installing an MGB fa iled pump 

sensor and vacuum switch wiring, installing an MGB oil auto bypass system, activating AMS 7. 1 

software to show a new MGB "OlL OUT" visual warning, updating the EGPWS software to 

include an aural annunciation of a complete oil pressure loss condition, and inserting an RFM 

Supplement into the applicable RFM. 

This proposed AD is prompted by one accident and one in-service oil leakage incident where 

it was discovered during subsequent investigations that the pilot failed to activate the bypass 

valve within 5 seconds of the oil pressure dropping below 35 psi, as required by the RFM. Both 

accident and incident investigations found that the pilot activated the bypass valve well beyond 

the 5 seconds. 

The manual operation of the bypass valve within 5 seconds of the oil pressure dropping below 

35 psi has proven not to be a realistic expectation. The MOB fai led pump sensor and vacuum 

switch wiring is a system that will detect a loss of oil pump scavenge vacuum in the input 

Page l of 3 
modul e and alert the pilot if the low oil pressure is the result of a fa iled oil pump. The MG B oil 

auto bypass system eliminates the need for the pilot to manually switch the bypass valve when 

the o il pressure drops be low 35 psi. The AMS software upgrade is to automate the bypass valve 

such that it will switch into oil cooler bypass mode and to alert the pilot that the low oil pressure 

may be the result o f a fail ed o il pump. Knowing the low oil pressure is the result of a fa iled oil 

pump and not due to oil leakage will allow the pilot to switch the bypass valve out of bypass 

mode to allow cooling of the oil. When the oil is not cooled, the hot oil may cause the gearbox to 

overheat. The EGPWS software change provides a new aural warning of a complete oil pressure 

loss. 

If NO, we don' t agree because 

ISSUE 2: Select one ofthe.following: 

If other, explain: 

Commenter(s): 

What change to the AD action is requested? 

Why is the change requested or how is it justified? 

Do we agree? 

If YES, we agree because Make the following c hanges to the AD: 

If PARTIALLY AGREE, we agree with because We disagree with because 

Make the following changes to the AD: 

If NO, we don' t agree because 

For additional issues, double-click here 

Page2of 3 
Signature Section 

Signature indicates concurrence with this action. 

Originating Office Tracking No.: SPO 170380-R 

Date 

/0-$--14 

Date 

C..05 

Page 3 of3 
Sikorsky supports the issuance of the AD. but has the fo llowing clarifications in red 

italics: 

·· Discussion 

We propose to adopt a new AD for Sikorsky Model S-92A helicopters. This proposed 

AD would require, depending on the helicopter's serial number. installing an MGB fa iled 

pump sensor and vacuum switch wiring. installing an MGB oil auto bypass system. 

activating AMS 7.1 software to show a new MGB " OIL OUT" visual warning. updating 

the EGPWS software to inc lude an aural annunciati on of a complete oil pressure loss 

condition. and inserting an RFM Supplement into the applicable RFM. 

This proposed AD is prompted by one accident and one in-service oil leakage incident 

in the 2008 - 2009 timeframe where it was discovered during subsequent in vesti gations 

that the pilot fa iled to activate the bypass va lve within 5 seconds of the oil pressure 

dropping below 35 psi. as required by the RFM . Both accident and incident investigations 

found that the pilot activated the bypass valve' ell beyond the 5 seconds. 

The manual operation of the bypass va lve within 5 seconds of the oil pressure dropping 

below 35 psi has proven not to be a rea listic expectation. The MGB fai led pump sensor 

and vacuum switch wiring is a system that will detect an oil pressure drop a loss o.f oil 

pump scavenge vacuum in the input module and alert the pilot if the low oil pressure loss 

o.f vacuum is the result of a fa iled oil pump. The MGB oil auto bypass system eliminates 

the need for the pilot to manual ly switch the bypass valve when the oil pressure drops 

below 35 psi. The AMS software upgrade is to automate the bypass valve such that it 11'ill 

switch into oil cooler bJ pass mode and to alett the pilot that the lovr oil pressure loss o.f 

pump sca1·enge vacuum may be the result of a failed oil pump. Knowing the low oil 

pressure loss of vacuum is the result of a fa il ed oil pump and not due to oil leakage will 

allow the pilot to switch the bypass va lve out of bypass mode to allow cooling o./'the oi l. 

When the oil is not cooled. the hot oil may cause the input module seals to fa il allowing 

an eJteessive amount of oil to leak resulting in failure of the MGB gearbox to overheat. 

Accordingly, the RFM revision contains a procedure for avoiding the overheating 

situation by directing the pi/otto bring the engine on the af{ected side of the pumpfailure 

to idle, siOII'ing the speed o_{the aircraf t, and ensuring there is a slight nose-up pitch of 

the aircraft. There have been se,.·eral incidents of a pump fai lure where the oil had the 

potential to reach a high enough temperature to damage the seals. The EG PWS software 

change provides a new aural warning of a complete oil pressure loss . .. 

The incidents mentioned were hi ghly un li kely to reach the seal damage, loss of oil. stage. 

An improved input modul e liner program has replaced the majori ty of the fleet and has 

mitigated th is issue. Additiona ll y. the pi lot wil l see secondary indications (e levated MGB 

oil temperatures and vaporization of the MGB paint [odor and smoke]) prior to the 

temperatures where seal damage is li kely. Even in the extremely improbable case of 

complete loss of oil. the MGB is capable of operati on for a time sufficient to perform an 

emergency landing.