Gulfstream Aerospace LP ¤ PO Box 1036 ¤ Airport City 70100 ¤ ISRAEL 

Tel: +972-3-935-6624 ¤ Fax: +972-3-935-6750 

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6/26/2012 GALP Ref: FAA/12130/CG 

 

Mr. Victor Wicklund 

Manager, Propulsion & Mechanical Systems Branch 

Transport Standards Staff 

U.S. Department of Transportation 

Federal Aviation Administration 

Transport Airplane Directorate 

1601 Lind Avenue, S.W. 

Renton, Washington 98057-3356 

Dear Mr. Wicklund: 

Gulfstream Aerospace Limited Partnership (GALP) is in receipt of your acknowledgement letter 

dated July 18, 2012 regarding our petition for exemption via letter FAA/12107/CG (docket number 

FAA-2012-0553). Accordingly, GALP provides the following additional information as requested: 

With regard to FAA’s item 1 – 

Regarding “gas temperature indicator” and associated limits and rules requiring relief – 

GALP agrees that FAA’s interpretation as-stated in the acknowledgement letter is correct; we 

summarily accept FAA’s position regarding this interpretation. 

GALP initially sought relief from §§ 25.1305(c)(1) and 25.1309(d) due to an understanding that the 

cited conditions required such relief. GALP now realizes through FAA’s clarification that relief from 

§§ 25.901(b)(1) and 25.1549(a) are appropriate due to the conditions of an ITT redline below engine 

TCDS limits and higher bleed demand during WAI System warm-up. To that end, Honeywell and 

their Type Certificate issuing office have concluded that the cited over-bleed risk will not constitute a 

unacceptable condition and will provide appropriate substantiation in support of this exemption. 

With regard to FAA’s item 2 – 

Negligible addition to overall fleet risk / limited number of airplanes to be delivered during exemption 

period – 

GALP understands FAA’s need to understand the full import of fleet size effect given the numbers of 

operational hours per airplane per year. GALP respectfully holds that corporate production rate 

projections are protected for proprietary and public trading regulatory compliance purposes. 

However, GALP may conservatively state, for the purpose of FAA’s express need of understanding 

fleet risk in terms of total fleet experience, that aggregate fleet operational hours during the 

foreseeable 2-year period of the exemption would be approximately 22,428 hours. This aggregate 

projection is based on the history that was previously stated in GALP’s petition for exemption: a highusage rate for Gulfstream Mid-Cabin airplanes of about 600 hours per year and that the more typical 

usage rate is approximately 400 hours per year. 

With regard to FAA’s item 3 – 

Airplane Flight Manual (AFM) procedures including prohibition against operation in WAI System 

auto-mode – 

As noted, GALP stated that the condition of the requested exemption would be appropriately 

stressed during pilot type rating and training activities to ensure crew awareness of the extremely 

remote potential for an exceedance warning. 
Gulfstream Aerospace LP ¤ PO Box 1036 ¤ Airport City 70100 ¤ ISRAEL 

Tel: +972-3-935-6624 ¤ Fax: +972-3-935-6750 

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In support of FAA’s request for a more detailed description of the relevant flight manual procedures 

and flight-crew training features and to assure that the stated conclusion of crew awareness remains 

valid, GALP provides the following: 

The AFM limitations and procedures were revised to simplify the operation of wing anti-ice so the 

pilots can feel free to use WAI at any time. The limitations define icing conditions and there is a 

stated requirement that WAI must be on for takeoff if in icing conditions or icing conditions are 

anticipated. The procedures were revised such that the flight crews are prompted to select WAI and 

EAI ON "as required" during ground operations thru the Line Up checklist. Once airborne, the After 

Takeoff, Climb Transition, Before Descent and Descent Transition checklists all have checklist items 

prompting the flight crews to select WAI and EAI ON "as required". 

There are no WAI specific procedures nor are there any procedures that regulate ITT by throttle 

position. 

For training, we have told Flight Safety to revise their Ice and Rain training material to discuss the 

following: 

1. Describe the current ITT limits (928 deg C and 946 deg C) as conservative. They will be updated 

within 18-24 months to the Engine TCDS ITT limits of 955 deg C and 970 deg C when the fleet will 

be updated with new FADEC hardware and software. 

2. Describe the new SPIC inhibition for 2 minutes after WAI is selected ON to allow the wing to 

reach the warm state. 

3. For takeoff into icing conditions, the WAI should selected ON at least 2 minutes prior to takeoff to 

allow the wings to warm up. The engine start checklist has a step to select WAI ON after the 

engines are started. The Before Takeoff checklist has two steps that involve WAI use. The first step 

is to "check/as required" with a follow up step to verify the WAI wing temperatures have reached 130 

deg F +/- 10 prior to takeoff if WAI is to be used. 

4. Describe that best practices when using WAI is when thrust is at climb power or lower. However, 

there is no prohibition to select WAI ON at any thrust setting because GALP's analysis shows that 

the probability of an ITT exceedance is extremely remote. 

5. If, by chance, an ITT exceedance occurs, follow AFM procedures to reduce thrust. 

With regard to FAA’s item 4 – 

WAI System – failure probabilities (Uncommanded activation) - system switched off – 

GALP has provided FAA with a detailed WAI System description and System Safety Analysis as of 

July 13 and 14, respectively (by email with attachment to Tom Groves and Mike McRae) as part of 

the normal TC validation package. Mr. McRae has confirmed that the appropriate material has been 

provided. 

With regard to FAA’s item 5 – 

Adequacy of engine margins and assurance and maintenance of same during the two year 

exemption period – 

GALP acknowledges FAA’s request to ensure that adequate engine margins are demonstrated to 

CAAI’s satisfaction as a part of the final TC process for approved environmental and operating 

conditions. 

GALP is working with CAAI to ensure that the appropriate documentation is provided to substantiate 

that the existing ITT/N2 margins in support of certification and FAA validation, and in turn thereby this 
Gulfstream Aerospace LP ¤ PO Box 1036 ¤ Airport City 70100 ¤ ISRAEL 

Tel: +972-3-935-6624 ¤ Fax: +972-3-935-6750 

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exemption. CAAI will formally accept this additional documentation once reviewed and found to 

meet their requirements. 

Respectfully, 

Charly Gaber 

GALP Certification PE 

Charly.gaber@gulfstream.com

972 3 935 6627