01/26/2010 16:39 8163294106 SAD PAGE 02/04 

& 

U.S, Department 

of Transportation 

Federal Aviation 

AdmlnUtration 

Small Airplane Directorate 

901 Locust 

Kansas City, MO 64106 

Mr. Kim Hackctt 

DOA Administrator 

Cessna Aircraft Company 

One Cessna Boulevard 

Wichita, KS 67277-7704 

Dear Mr. Hackett: 

We are enclosing a grant of your petition submitted on November 4,2009, requesting an 

exemption with time-limited conditions from the requirements of 14 CFR part 23, 

§§ 23.1321(b), 23.1549(a), (b), and (c). The exemption allows Cessna to type certificate the 

Cessna model 525C airplanes without oil pressure and temperature indications specified in 

the rule. If you have any questions, please contact Mr. Pete Rouse at the above address or 

call him on 816-329-4135. 

Sincerely, 

Q^-Kim Smith 

Manager, Small Airplane Directorate 

Aircraft Certification Service 

Enclosure 
01/26/2010 16:04 8163294105 SAD PAGE 02/11 

Exemption No. 9998 

UNITED STATES OF AMERICA 

DEPARTMENT OF TRANSPORTATION 

FEDERAL AVIATION ADMINISTRATION 

WASHINGTON, DC 20591 

In the matter of the petition of 

CESSNA AIRCRAFT COMPANY 

for an exemption from §§ 23.1321(b), 

23,1549(a),(b),and(c) 

of Title 14, Code of 

Federal Regulations 

Regulatory Docket No. 2009-1064 

GRANT OF EXEMPTION 

By letter dated November 04,2009, Mr. Kim Hackett, Cessna Aircraft Company, One 

Cessna Boulevard, P.O. Box 7704, Wichita, Kansas 67277-7704 petitioned for an exemption 

with time-limited conditions from §§ 23.1321(b), 23,1549(a), (b), and (c) of Title 14 of the 

Code of Federal Regulations (CFR) to permit type certification of the Cessna model 525C 

airplanes without oil pressure and temperature indications specified in the rule. The proposed 

exemption would permit relief from the requirements for arrangement, visibility and colors for 

the engine oil temperature and pressure indications for the model 525C airplanes. The current 

design of the engine oil temperature and pressure indications of the model 525C airplanes 

provides conflicting color indications in certain operational regimes. The proposed 

exemption, if granted, would permit type certification approval of the model 52 5C airplanes 

with this non-compliant type design for a limited time. 

The petitioner requests relief from the following regulation[s]: 

Sections 23.1321(b), 23.1549(a), (b), and (c), in pertinent part, requires certain 

arrangement, visibility and colors for the engine oil temperature and pressure indications. 

The petitioner supports its request with the following information: 

Cessna Aircraft Company requests an exemption with time-limited conditions from 

the requirements of 14 CFR § 23.1321(b) and 14 CFR § 23.1549(a), (b), and (c) for 

tlie mode] 525C to the extent necessary to allow type certification of the Cessna model 

525C airplanes with the current engine oil pressure and temperature displays. As a 

condition for granting the requested time-limited exemption, Cessna Aircraft will 

design and certify dual scale engine oil pressure and temperature displays that are 
01/26/2010 16:04 8163294106 SAD PAGE 03/11 

compliant with the current FAA interpretation of 14 CFR § 23.1321(b) and 14 CFR 

§ 23.1549(a), (b), and (c) within 15 months of the granting of this exemption. Cessna 

Aircraft will provide a service bulletin to all field aircraft after certifying the new 

display. 

Cessna acknowledges that this petition was not submitted in accordance with the 120-

day requirement of 14 CFR § 11.63(d). The reason for this delayed request is that the 

applicable design review and discussion that revealed the airpleine was not in direct 

compliance with requirements of the rule was not conducted until late in the 

certification, program. Cessna Aircraft Company consequently requests that the 

publication and comment period requirements of 14 CFR § 11,85 be waived. 

14 CFR Reference 

14 CFR S 23.1321: Arrangement and visibility. 

(b) For each multiengine airplane, identical powerplant instruments must be located so 

as to prevent confusion as to which engine each instrument relates. 

14 CFR $ 23.1549: Powerplant and auxiliary power unit instruments. 

For each required powerplant and auxiliary power unit instrument, as appropriate to 

the type of instruments— 

(a) Each maximum and, if applicable, minimum safe operating limit must be marked 

with a red radial or a red line; 

(b) Each normal operating range must be marked with a green arc or green line, not 

extending beyond the maximum and minimum safe limits; 

(c) Each takeoff and precautionary range must be marked with a yellow arc or a yellow 

line 

Background 

The current installation of the Rockwell Collins Proline 21 system on the model 525C 

airplane consists of a single scale display for LH and RH oil pressure and a single 

scale display for LH and RH oil temperature. Similar installations are installed and 

certified on other part 23 Cessna aircraft including the models 525, 525A, and 525B 

that have incorporated the Collins Proline 21. 

The single scale display for the engine oil pressure and tempemture has considerable 

field experience; the model 525 Jiirplane, which incorporates the Proline 21 system, 

has over 426,000 flight hours, the model 525A has over 517,000 flight hours, and the 

model 525B has over 250,000 flight hours. This is approximately 1.2 million flight 

hours for this type of display. Ttiere have been no reports of issues in the field related 

to how the engine oil pressures or temperatures are displayed. 
01/26/2010 16:04 8163294106 SAD PAGE 04/11 

Current Design: Single Scale Oil Pressure Display: 

The current model 525C oil pressure indication is displayed on the Multifimction 

Display (MFD), which is centrally located on the instrument panel. The visibility and 

location of the oil presswe display is similar to other previously certified Citation 

aircraft, and has been evaluated during flight testing of the model 52 5C. The primary 

display provides a single analog scale for botla the LH and RH engines, with a pointer 

indicating the respective engine oil pressure. This is the primary indication of oil 

pressure to the crew. When the "OIL DISPLAY ENABLE" discrete is selected via the 

maintenance panel, a digital readout is displayed for each engine, below the analog 

scale, with a resolution of 1 PSI (refer to Figure 1). 

Normal Display Oil Display Enabled 

Figure 1: Current Engine Oil Displays 

When, the "OIL DISPLAY ENABLE" discrete is not selected, the digits are not 

displayed on the MFD, unless a limit is exceeded. Regardless of the "OIL DISPLAY 

ENABLE" discrete setting, if a caution limit is reached, the digits will be displayed 

and the digits and pointer will be yellow, and will flash for five seconds. If a warning 

limit is reached, the digits will be displayed and the digits and pointer will be red and 

flash for five seconds (refer to Figure 2). 
01/26/2010 15:04 8163294106 SAD PAGE 05/11 

Figure 2: Oil Display with limits exceeded 

The oil pressure analog scale has a range of 0 to 150 PSI. The caution and warning oil 

pressure limits are transmitted by the Full Authority Digital Electronic Control 

(FADEC), and are as follows: 

Upper Warning Limit: 130 PSI 

Upper Caution Limit: 120 PSI (5 minute operational limit) 

For N2 > 80 percent: 

• Lower Warning Limit: 40 PSI 

o If this limit is reached, N2 should be reduced below 80 percent per 

AFM 

For N2 < 80 percent 

• Lower Caution Limit: 30 PSI (5 minute operatiotial limit) 

• Lower Warning Limit: 23 PSI 

As discussed above, the scale limits for oil pressure are dependent on engine N2 

speed. The analog scale is a static display with color bands representing the limits for 

N2 < 80 percent, however, the pointers and digits reflect the limits for the current N2 

speed. Per the model 525C Aircraft Flight Manual (AFM), pilot actions are based on 

the pointer and digit color and indication, not the color of the oil pressure scale. If N2 

> 80 percent, and the low limit is reached, per AFM procedures, the crew is instructed 

to reduce N2 to < 80 percent. 

In addition to the oil pressiu-e display, a red "OIL PRESSURE LOW LrR" Crew Alert 

System (CAS) message is displayed accompanied by a Master Warning and Aural 

Tone whenever the oil pressure exceeds the low oil pressure limits as transmitted by 

the FADEC. 
01/26/2010 16:04 8163294106 SAD PAGE 06/11 

Current Design: Single Band Oil Temperature Display: 

The current model 525C oil temperature indication is displayed on the MFD, which is 

centrally located on the instrument panel. The visibility and location of the oil 

temperature display is similar to other previously certified Citation aircraft, and has 

been evaluated during flight testing of the model 525C. The primary display provides 

a single analog band for both the LH and RH engines, with a pointer indicating the 

respective engine oil temperature. This is the primary indication of oil temperature to 

the crew. When the "OIL DISPLAY ENABLE" discrete is selected via the 

maintenance panel, a digital readout is displayed for each engine, below the analog 

band, with a resolution of 1 °C (refer to Figure 1). 

When the "OIL DISPLAY ENABLE" discrete is not selected, the digits are not 

displayed on the MFD, imless a limit is reached. Regardless of the "OIL DISPLAY 

ENABLE" discrete setting, if a caution limit is reached, the digits will be displayed 

and the digits and pointer will be amber, and will flash for five seconds. If a warning 

limit is reached, the digits will be displayed and the digits and pointer will be red and 

flash for five seconds (refer to Figure 2). 

The oil temperature analog scale has a range of 0 to 160 °C, The caution and warning 

oil temperature limits are defined by the FADEC, and are as follows: 

For N2< 80 percent: 

• Upper Warning Limit: 149 °C 

• Upper Caution Limit: 135 °C (5 minute operational limit) 

• Lower Caution Limit: 10 °C 

For N2> 80 percent: 

Upper Warning Limit: 135 'C 

Lower Warning Limit: 10 "C 

As discussed above, the scale limits for oil temperatiu-e are dependent on engine N2 

speed. The analog band is a static display with color bands representing the limits for 

N2 < 80 percent; however, the pointers and digits reflect the FADEC limits for the 

current N2 speed. Per the model 525C AFM, pilot actions are based on the pointer 

and digit color and indication, not the color of the oil temperature band. For oil 

temperatures < 10 *C, per the AFM, the crew is instructed to not advance the throttles 

above 80 percent N2 imtil the oil temperature has increased above 10 °C. 

Proposed Design: Dual Scale Oil Displays: 

The proposed model 525C engine oil pressure and temperature displays will include a 

dual scale indication for the engine oil pressure and oil temperature (refer to Figure 3), 

5 
01/26/2010 16:04 8163294106 SAD PAGE 07/11 

The left and right scales will be dynamic and updated based on the engine N2 speed at 

the limits as transmitted by the FADEC and defined by the engine manufacture. 

Besides separate dynamic scales for LH and RH engines, the operation of the system 

will be the same as described above for tlie current system. 

Figure 3: Proposed Dual Scale Oil Display 

Petition 

Cessna Aircraft Company requests an exemption with time-limited conditions from 

the requirements of 14 CFR § 23.1321(b) and 14 CFR § 23.1549(a), (b) and (c) for the 

model 525C for tlie engine oil pressure and temperature displays on the model 525C, 

This exemption would allow type certification of the Cessna model 525C airplanes 

with the current engine oil pressure and temperature displays, while permitting 

adequate time to design and certify' the proposed dual scale display in order to 

establish full compliance with the latest interpretation of the requirements of 14 CFR 

§ 23.1321(b) and 14 CFR § 23.1549(a), (b), and (c). 

As a condition for granting the requested exemption, Cessna Aircraft will design and 

certify engine oil pressure and temperature displays that are fully comphant with the 

latest interpretation of 14 CFR § 23.1321(b) and 14 CFR § 23.1549(a), (b), and (c) 

within 15 months of the granting of this exemption. 

Tlie next scheduled version of the display software from Collins (v2.0) has a 

certification schedule for TSO receipt by end of year 2010. Due to current manpower 

constraints at Collins it is not feasible to incorporate the new oil displays prior to v2.0 

without significantly delaying v2-0. Collins display software v2.0 is required for 

EASA certification and any delay in EASA certification could result in significant 

financial penalties for Cessna Aircraft Company, 

Cessna Aircraft will provide a service bulletin to all model 525C field aircraft after 

certifying the new display. 
01/26/2010 16:04 8163294105 SAD PAGE 08/11 

Ftirther, prior to the installation of the service bulletin to install the new engine oil 

pressure and temperatiu'e displays, Cessna Aircraft will include notes in the Airplane 

Flight Manual (AFM) to help clarify the band and pointer colors. The notes will be 

removed once the service bulletin is installed. Tlie essence of the note will be to 

address the following items; the specific wording is to be agreed upon between Cessna 

and FAA as part of the AFM approval process. 

• The color bands on the vertical tape for oil temperature and pressure are 

for engine setting below 80 percent N2. 

• For throttle settings at or above 80 percent N2 the engine oil pressure 

indication will turn red below 40 psi indicating that the engine has 

exceeded its operational limits even though the pointer is not in the red 

band of the vertical tape. There is no low pressure cautionary (yellow) 

band for N2 speedg above 80 percent. 

• For throttle settings at or above 80 percent N2 the engine oil 

temperature indication will turn red above 135 *C and belowlO "C 

indicating that the engine has exceeded its operational limits even 

though the pointer is not in the red band of the vertical tape. There is 

no oil temperature cautionary (yellow) band for N2 speeds above 80 

percent. 

Petitioner's Public Interest Statement 

Cessna Aircraft Company states that granting this exemption would be in the public 

interest for the following reasons; 

1. The current engine oil pressure display allows for safe operation of the engine 

within its operational limits as shown by the 1.2 million flight hours of similar 

displays on other model 525 series aircraft. The current display provides four 

visual cues and one auditory cue that will alert the pilots that an engine oil 

pressure limit has been exceeded. 

• The pointer for tliat engine will turn the appropriate warning color. 

• The digital readout for that engine will be displayed in the appropriate 

color, flashing for five seconds. 

• For low oil pressure a CAS message "OIL PRESSURE LOW L-R" will 

be displayed. 

• For low oil pressure the Master Warning annunciator will be 

illuminated with an associated aural warning tone. 

2. The current engine oil temperature display allows for safe operation of the 

engine within its operational limits as shown by the 1.2 million flight hours of 

similar displays on other model 525 series aircraft. The current display 
01/26/2010 15:04 8163294106 SAD PAGE 09/11 

provides two visual cues that will alert the pilots that an engine oil temperature 

limit has been exceeded. 

• The pointer for tl-iat engine will turn the appropriate warning color. 

• Tlie digital readout for that engine will be displayed in the appropriate 

color, flashing for five seconds. 

3. Similar engine oil pressure and temperature displays are currently in use on 

other model 525 series aircraft models with over 1.2 million flight hours of 

field service experience. There have been no reports by the pilots of confiasion 

in reading and understanding the engine oil pressure or temperature displays 

and no reports of engine 'damage caused by misinterpreting the engine oil 

displays. Therefore field experience has shown that the cvirrent engine oil 

displays do not cause a hazard to the aircraft. 

4. The denial of this petition for exemption would result in the delay of the 

certification of model 525 C airplanes for approximately 15 months. Cessna 

would experience a loss of revenue of at least $140 million in 2010 and $120 

million in 2011 due to this delay. This could also result in numerous aircraft 

order cancellations increasing the fmancial loss significantly. This would also 

result in the loss of revenue for partners and suppliers and the potential need 

for workforce reductions, all of which would be counter to the public interest. 

Cessna's customers have made utilization plans based on the agreed upon delivery 

schedule of these airplanes. Delay in the delivery date due to the redesign and retrofit 

of the engine oil displays would impose significant financial penalties upon our 

customers and their businesses without a commensurate safety benefit, which is also 

counter to the public interest. 

Notice and Public Procedure Provided 

A summary' of the petition was published on December 29, 2009 (74 FR 68914). No 

comments were received. 

The FAA's analysis is as follows: 

To obtain this exemption, the petitioner must show, as required by 14 CFR part 11, 

§§ 11.81(d) and 11.81 (e): "(1) the reasons why granting your request would be in the public 

interest; that is, how it would benefit the public as a whole, and (2) the reasons why granting 

tte exemption would not adversely affect safety, or how the exemption would provide a level 

of safety at least equal to that provided by the rule from which you seek the exemption." 

The FAA has carefully reviewed the information contained in the petitioner's request for 

exemption, 

S 
01/26/2010 16:04 8163294106 SAD PAGE 10/11 

The FAA agrees with the petitioner's request for the following reasons: 

1. The current engine oil pressure display allows for safe operation of the engine within 

its operational limits as shown by the 1.2 million flight hours of similar displays on 

other model 525 series aircraft. The current display provides four visual cues and one 

auditory cue that will alert the pilots that an engine oil pressure limit has been 

exceeded. 

o The pointer for that engine uill turn the appropriate warning color. 

o Tlie digital readout for that engine will be displayed in the appropriate color, 

flashing for five seconds. 

o For low oil pressure a CAS message "OIL PRESSURE LOW I^R" will be 

displayed. 

o For low oil pressure the Master Wanting annunciator will be illuminated with an 

associated aural warning tone. 

2. The current engine oil temperatui-e display allows for safe operation of the engine 

within its operational limits as shown by the 1.2 million flight hours of similar 

displays on otiier model 525 series aircraft. The current display provides two visual 

cues that will alert the pilots that an engine oil temperature limit has been exceeded. 

o The pointer for that engine will turn the appropriate warning color. 

o The digital readout for that engine will be displayed in the appropriate color, 

flashing for five seconds. 

3. Similar engine oil pressure and temperature displays are currently in use on other 

model 525 series aircraft models with over 1.2 million flight hours of field service 

experience. Tliere have been no reports by the pilots of confusion in reading and 

understanding the engine oil pressure or temperature displays and no reports of engine 

damage caused by misinterpreting the engine oil displays. Therefore field experience 

ha5 shown that the current engine oil displays do not cause a hazard to the aircraft. 

4. The denial of this petition for exemption would result in the delay of the certification 

of model 525C airplanes for approximately 15 months. The economic impact to 

Cessna Aircraft Corporation would be severe and result in significant reductions in 

Cessna's workforce. Additionally, the economic impact to Cessna's suppliers and 

customers would also be significant. 

The FAA's Decision 

In consideration of the foregoing, I find that a grant of exemption is in the public interest. 

Therefore, pursuant to the autiiority contained in 49 U.S.C. §§ 40113 and 44701, delegated to 

me by the Administrator, Cessna Aircraft Company is granted an exemption with time-limited 

conditions from §§ 23.1321(b), 23.1549(a), (b), and (c) to the extent necessary to allow type 
01/26/2010 16:04 8163294106 SAD PAGE 11/11 

certification of the Cessna model 525C airplanes with engine oil temperature and pressure 

indications not in compliance with the requirements of §§ 23.1321(b), 23.1549(a), (b), and (c) 

as they relate to the arrangement, visibility and colors. For the model 525C airplanes, this 

exemption is subject to the following conditions and limitations: 

Conditions and Limitations 

1. Cessna Aircraft Company must certify and incorporate into the production line 

requirements engine oil temperature and pressure indications fully compliant with 

the requirements of §§ 23.1321(b), 23.1549(a), (b), and (c), into the model 525C 

airplanes no later than April 30, 201,1. 

2. Cessna Aircraft Company miujt retrofit the model 525C airplanes delivered tmder 

the terras of the exemption with the new engine oil temperature and pressure 

indications described in Condition 1 above no later than April 30,2012. 

3. Until the incorporation of the changes required in the above Conditions 1 and 2 of 

this exemption have been completed, Cessna Aircraft Company add to the airplane 

flight manual (AFM) a description of the indications and their conflicting color 

guidance, and the necessary instructions for properly interpreting the oil pressure 

and temperature indications. 

4. For airplanes subject to Condition 2 of this exemption, the operating limitations 

section of the airplane flight manual (AFM) must include tlie following statement: 

"No person may operate this airplane after April 30, 2012, unless the oil 

pressure and temperature indications have been modified in accordance with 

the terms of Exemption No. 9998." 

This statement may be removed from the AFM after the required modification has 

been made. 

This exemption terminates on April 30,20 H, unless sooner superseded or rescinded. 

Issued in Kansas City, Missouri on January 26,2010. 

John Colomy 

Acting Manager, Small Airplane Directorate 

Aircraft Certification Service 

10