Petition for Temporary Exemption With Respect to FAR 23.1549(b)

DHC-6 Series 400 (Twin Otter)

Revision IR (P3) (25 November 2011) Page 1 of 7 Viking Air Limited

Summary

Viking Air Limited (VAL) requests a temporary exemption from the requirements of 14 CFR 23.1549(b) for

the VAL DHC-6 Series 400 (Twin Otter) to the extent necessary to allow FAA type certification of the

aircraft with the current Honeywell Primus Apex

TM

engine displays.

As conditions for granting the requested temporary exemption, VAL commits to the following:

1. VAL working with Honeywell International Inc. will design and certify an engine display

configuration on Primus Apex

TM

for the DHC-6 Series 400 specific to meeting the FAA normal

engine display color requirements as specified in FAR 23.1549(b).

2. This design and certification will be accomplished within fifteen (15) months of granting this

exemption.

3. VAL will provide a service bulletin to all US-registered field aircraft after certifying the new display

configuration.

Regulatory Reference -- Section 23.1549 Powerplant and Auxiliary Power Unit Instruments

(Amendment 25-45)

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; and

(d) Each engine, auxiliary power unit, or propeller range that is restricted because of excessive

vibration stresses must be marked with red arcs or red lines.

Background

The Honeywell Primus Apex

TM

EFIS engine display design as implemented on the Viking DHC-6

Series 400 does not comply with FAR 23.1549(b) with respect to the use of white instead of green to

display normal operating conditions. As well, some engine parameters are only provided digitally.

Torque and T5 are provided both digitally and graphically.

The DHC-6 Series 400 is currently undergoing FAA certification as a validation of Transport Canada Civil

Aviation (TCCA) Type Certificate A-82 under the Bilateral Aviation Safety Agreement (BASA). The

DHC-6 Series 400 achieved certification in Canada and in Europe in 2010.

The integration on Apex

TM

and in the cockpit with CAS messages, dynamic caution and warning engine

display ranges, and integration with the Master Caution / Warning (MCW) System achieves a high level of

safety that ensures immediate pilot awareness of caution or warning conditions and good awareness and

visibility of normal operating conditions and trends. The integrated cockpit environment developed

around Honeywell’s Primus Apex

TM

also enhances the availability of engine information on both the pilot

and co-pilot’s Primary Flight Displays (PFD’s). The overall integration of the cockpit, the caution and

warning level CAS messages available with respect to engine torque and T5 displays, and the associated

digital display inverse video caution and warning level display design have been demonstrated to be
Petition for Temporary Exemption With Respect to FAR 23.1549(b)

DHC-6 Series 400 (Twin Otter)

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effective in providing the crew with current operating information, are effective in crew alerting, and

achieve a high degree of safety. It is also noted that ELOS are part of both the Transport Canada and

EASA certifications of the DHC-6 Series 400, and that the installation design is consistent with advisory

material and design guidance in FAA AC 20-88A, FAA AC 23.1311-1B, .FAA AC 23-23,

GAMA Publication No. 12, and FAA AC 25-11A.

Discussion

The DHC-6 Series 400 aircraft incorporates the Honeywell Primus Apex

TM

integrated avionics suite and

an “all-glass”, fully integrated cockpit. Primary flight information is indicated to the crew on the pilot’s

Primary Flight Display (PFD) and the copilot’s PFD. Engine displays are indicated on each PFD in a 1/6

display segment that includes semi-arc graphical and digital displays for Torque (TRQ) and turbine

temperature (T5). All of the displays make extensive use of colour to ensure that out-of-limit conditions

quickly become apparent to the pilot.

Figure 1 shows an engine display in the normal range. When the Torque and T5 pointers are in the

normal range (within the white band) the underlying pie-sector is grey. The corresponding digital value is

displayed in white, with a black background.

Figure 1 Engine Display

Figure 2 shows the display during a torque exceedance. The pointer is beyond the normal range (within

the red band) and the underlying pie-sector is red. The corresponding digital torque value is displayed in

inverse video (white numerals on a red background).
Petition for Temporary Exemption With Respect to FAR 23.1549(b)

DHC-6 Series 400 (Twin Otter)

Revision IR (P3) (25 November 2011) Page 3 of 7 Viking Air Limited

Figure 2 Engine Window (Torque Exceedance)

With respect to FAA Advisory Circular AC23.1311-1B (Installation of Electronic Displays in Part 23

Airplanes), the guidance and acceptable means of compliance in Section 9.0 and its sub-sections of the

Advisory Circular are followed. The following is noted:

a. 9.1 (General) to 9.3 inclusive (Loss of Critical Powerplant Information) -- The guidance in these

sections is followed, where applicable.

b. 9.4 (Direct-Reading Alphanumeric-Only Displays) – Engine parameters for which trends are

important are displayed in both graphically and digitally.

c. 9.5 (Marking of Powerplant Parameters) – VAL has adopted alternate methods of marking

electronic powerplant display of normal operating conditions as provided for in FAA Advisory

Circular AC 20-88A and as acknowledged in Section 9.5 of AC23.1311-1B. Extensive evaluation

of this configuration was completed by VAL and TCCA.

The following characteristics of the DHC-6 Series 400 engine displays as embodied on Apex area noted

and are consistent with the guidelines in FAA AC 23.1311-1B:

a. All required powerplant parameters for engine start, power setting and for monitoring engine

power and associated limiting conditions are provided by the installation design. It is noted that

with respect to Torque and T5, there are no lower engine operating limits, the only limitations that

matter are exceedances that put the parameters in the upper caution or warning ranges.

b. No pilot action is required to display any engine parameter under normal operating conditions.

c. Caution and warning limits are graphically displayed for Torque and T5 with associated

FAR 23.1549 colour changes. Corresponding digital displays appear in inverse video with the

appropriate colour.

d. Torque and T5 comply with this guidance paragraph by providing information both graphically and

digitally. Torque and T5 are the key power setting and engine monitoring parameters.

Identification of abnormal conditions is facilitated and apparent to the flight crew under all

operating conditions.
Petition for Temporary Exemption With Respect to FAR 23.1549(b)

DHC-6 Series 400 (Twin Otter)

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e. The displays provide a clear indication of where a parameter is relative to a limit. In the DHC-6

Series 400 implementation, the limitation markings automatically change to correspond to the

limitation currently applicable to that phase of engine operation (Start, Idle, Take-off, Climb and

Cruise, and MCP for single engine operations).

f. Caution and warning limits for Torque and T5 are provided both on the displayed arc and in the

underlying pie-sector, they have been evaluated to be effective in informing the flight crew of the

associated engine conditions and trends, and to make caution and warning conditions

immediately apparent.

With respect to FAA Advisory Circular AC20-88A (Guidelines on the Marking of Aircraft Powerplant

Instrumentation [Displays]), the following is noted:

a. FAA AC 23.1311-1B points to FAA AC 20-88A with respect to the marking of powerplant

parameters on electronic displays (per Section 9.5 of AC 23.1311-1B).

b. Item 6c – Caution and warning exceedances for Torque and T5 are accompanied by associated

CAS messages (in colours compliant with FAR 25.1549) as well as inverse video and pie-sector

colour changes on the graphical displays.

c. Item 6d – This paragraph in AC20-88A specifically acknowledges the inherent flexibility of CRT

display design (and, by inference, the flexibility of display design for LCD flat-screen displays

used in Apex

TM

). Normal operating conditions need not necessarily be identified with coloured

markings, only abnormal conditions need to be so identified. In the case of the Torque and

T5 engine displays on the DHC-6 Series 400, both are displayed graphically, and have identified

caution and warning ranges that include colour changes and inverse video displays (also see

discussion for Item 6c above). This design provides for a high degree of visibility to the flight

crew when caution or warning limits are exceeded while still providing all information required in a

clearly visible and readable way for setting normal operating conditions.

In addition to the above-noted FAA AC’s, other industry and regulatory advisory and design guidance

material has been identified regarding use of color on engine displays. The following is pertinent to the

DHC-6 Series 400 implementation:

a. FAA AC 23-23 acknowledges General Aviation Manufacturers Association (GAMA)

Publication #12 (Recommended Practices and Guidelines for an Integrated Flightdeck / Cockpit

in a 14 CFR Part 23 (or equivalent) Certificated Airplane) as an acceptable means for showing

compliance with applicable requirements for electronic displays in Part 23 airplanes. This AC

also notes that “Guidance in AC 23.1311-1A, Installation of Electronic Displays in Part 23

Airplanes, Society of Automotive Engineers (SAE), and Radio Technical Commission for

Aeronautics (RTCA, Inc.) documents was used in developing the GAMA Publication #12”. This

GAMA publication was developed by a combined FAA and industry team.

b. GAMA Publication #12 specifies colour sets in Section 14.2. In the table associated with this

section, white is specified for “Scales and Associate Figures (Normal State)”.

c. FAA AC 25-11A, although intended for Transport Category aircraft, also supports use of white for

“scales, dials, tapes and associated information elements” (Table 11).

In addition to following design guidance in the above-noted government and industry documents, the

engine display design for the DHC-6 Series 400 was evaluated extensively by ground and flight test, as

well as through specification and design review, system safety assessment, and workload assessment.

This evaluation included the following:

a. Extensive integration testing of the displays at an engine system sensor level and at an aircraft

level.
Petition for Temporary Exemption With Respect to FAR 23.1549(b)

DHC-6 Series 400 (Twin Otter)

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b. Extensive flight testing evaluating the performance of the displays under a variety of day and

night conditions and for all phases of flight.

c. Demonstration of the effectiveness of the displays on the ground and in flight under a variety of

normal, abnormal and emergency operating conditions including day and night conditions, inflight

engine shutdowns and relights, numerous ground cart and battery engine starts, and a variety of

failure conditions such as loss of engine sensors and integrity of the graphical displays.

d. Pilot work load assessment (day and night).

e. System safety assessment.

f. Consideration of cockpit ergonomics including visibility of the displays under a variety of cockpit

lighting and operating conditions.

g. Suitability of display design for quick recognition by the pilot of abnormal operating conditions.

h. Consistent use of this philosophy for other engine parameter displays.

i. Comparison to other type designs in FAR Part 25 aircraft adopting similar engine display

features.

In addition to the above evaluations, considerations and display features, the engine display design also

includes a variety of visual and aural alerts when caution or warning conditions occur, including but not

restricted to the following:

a. Annunciation on the engine displays of various conditions such as start, idle, takeoff, and single

engine (S/E) operations.

b. Crew alerting system (CAS) messages corresponding to caution (amber) and warning (red)

conditions for various engine parameters including Torque and T5. The messages associated

with Torque and T5 are “Left Engine Torque”, “Right Engine Torque”, “Left Engine Temp”, “Right

Engine Temp” (all of these are warning level based on limiting value exceedances) and “Left

Engine Temp”, “Right Engine Temp” (these are caution level based on entry into the caution

range).

c. Integration of caution and warning conditions with the aircraft’s master caution/master warning

system.

Petition

Viking Air Limited (VAL) requests a temporary exemption from the requirements of 14 CFR 23.1549(b) for

the VAL DHC-6 Series 400 (Twin Otter) to the extent necessary to allow FAA type certification of the

aircraft with the current Honeywell Primus Apex

TM

engine displays.

As conditions for granting the requested temporary exemption, VAL commits to the following:

1. VAL working with Honeywell International Inc. will design and certify an engine display

configuration on Primus Apex

TM

for the DHC-6 Series 400 specific to meeting the FAA normal

engine display color requirements as specified in FAR 23.1549(b).

2. This design and certification will be accomplished within fifteen (15) months of granting this

exemption.
Petition for Temporary Exemption With Respect to FAR 23.1549(b)

DHC-6 Series 400 (Twin Otter)

Revision IR (P3) (25 November 2011) Page 6 of 7 Viking Air Limited

3. VAL will provide a service bulletin to all US-registered field aircraft after certifying the new display

configuration.

VAL has started a Phase 2 avionics upgrade program with Honeywell. This program is scheduled for

aircraft level certification by Transport Canada in late 2012. This program includes updates to the

Honeywell Apex and Apex Data Acquisition Unit (DAU) TSO’s in late 2012. The DAU and Apex updates

are required in order to develop the FAA configuration that provides an Apex option for the use of green

instead of white to display normal engine operating conditions. Therefore, a temporary exemption is

requested for fifteen (15) months.

Furthermore, in addition to the information already in the aircraft POH/AFM and the Apex Pilot Guide

provide details on the engine display color philosophy, VAL will provide any additional information and

clarification on the use of white instead green in the POH / AFM if required by the FAA for use during the

period of the exemption.

Petitioner’s Public Interest Statement

Viking Air Limited considers the granting of this exemption to be in the public interest for the following

reasons:

1. The integration on Apex

TM

and in the cockpit with CAS messages, dynamic caution and warning

engine display ranges, and integration with the Master Caution / Warning (MCW) System

achieves a high level of safety that ensures immediate pilot awareness of caution or warning

conditions.

2. The integrated cockpit environment developed around Honeywell’s Primus Apex

TM

also enhances

the availability of engine information on both the pilot and co-pilot’s Primary Flight Displays

(PFD’s).

3. The overall integration of the cockpit, the caution and warning level CAS messages available with

respect to engine torque and T5 displays, and the associated digital display inverse video caution

and warning level display design are effective in providing the crew with current operating

information, are effective in crew alerting, and achieve a high degree of safety.

4. ELOS are part of both the Transport Canada and EASA certifications of the DHC-6 Series 400.

5. The installation design is consistent with advisory material and design guidance in FAA

AC 20-88A, FAA AC 23.1311-1B, .FAA AC 23-23, GAMA Publication No. 12, and FAA AC

25-11A.

6. The DHC-6 Series 400 display configuration provides a higher level of safety than the legacy

DHC-6 Series 300 configuration that is currently approved in the United States under FAA Type

Certificate A9EA.

7. A significant amount of flight experience is available with the aircraft in the current Apex

configuration in development and certification testing, in cockpit workload evaluation, and, since

certification 2010, in production aircraft testing and operations in Transport Canada and EASA

jurisdictions in 2010. There have been no human factors, operational or safety issues identified

as a result of this experience related to the engine displays.

8. The denial of this petition for exemption would result in the delay of United States certification of

the airplane for approximately fifteen (15) months. VAL would experience a significant loss of

revenue as a result, as well US operators that have purchased the aircraft, including the US

Army, would be delayed in getting access to the aircraft. This delay may also result in aircraft
Petition for Temporary Exemption With Respect to FAR 23.1549(b)

DHC-6 Series 400 (Twin Otter)

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order cancellations and in loss of revenue for Viking’s US partners and suppliers including

Honeywell International.

9. US operators have made utilization plans based on the agreed upon delivery schedule. Delay in

the delivery date due to the redesign in engine display configuration would impose significant

financial and operational penalties upon VAL’s US DHC-6 Series 400 customers without a

commensurate safety benefit, this is counter to the public interest.