APGPerformance

RUNWAY ANALYSIS INTRODUCTION

The scope of this article is to help crews manage an informative decision when planning a heavy weight takeoff from mountainous terrain and/or obstacle burdened airports and the resulting action the crew, will or must, consider in the event of an engine failure during a critical phase of flight, takeoff and landing. Airplane Performance Group (APG) data not only provides a weight analysis but also publishes correct level-off heights, special departure maneuvers if required and assesses obstacles along the departure path not readily apparent from a SID. The article addresses: § Terminal Enroute Procedures (TERPS); Order

8260.3b § Advisory Circular AC120-91; “Airport Obstacle

Analysis.” The Advisory Circular describes acceptable methods and guidelines for developing takeoff and initial climb-out airport obstacle analysis and in-flight contingency procedures to comply with the intent of the regulatory requirements of 121/135 one-engine inoperative requirements. It is the culmination of combining certification performance requirements (FAR 25) with minimum obstacle clearance limits per 121/135 regulations.

§ APG’s “Runway Analysis as it is derived from the specific airplane’s AFM performance data.

§ APG’s Wet/Contaminated Runway Data. § Missed Approach considerations.

GENERAL

An APG Runway Analysis provides the means to determine a maximum allowable takeoff weight based upon: § Airport characteristics including airport elevation,

runway length and gradient, runway contaminant and obstructions along and within the takeoff flight path.

§ Environmental conditions including temperature, wind and pressure altitude.

§ Aircraft Configuration including power setting, flap setting, bleed configuration and MEL inoperative component(s).

SPECIFICS An APG Runway Analysis can effectively determine the maximum allowable takeoff weight limited by the most restrictive condition of the following weights: 1. Maximum Certified Structural Take-off Weight. 2. Climb Limit Weight: Most Limiting of;

2.4% Second Segment Climb 1.2% Final Segment Climb 2.1% Approach Climb Gradient

3. Field Length Limit Weight. Most limiting of; Accelerate Go Distance Accelerate Stop Distance All Engine Go + 15%

4. Obstacle Limit Weight. 5. Brake Energy Limit Weight. 6. Tire Speed Limit Weight. 7. One not readily apparent is a limiting weight based

upon wet/contaminated runway conditions upon which an aircraft’s AFM or supplement guide may either require AFM approved data as in Global and Challenger performance, or provide guidance as in supplementary information for the Gulfstream.

FAA TERMINAL ENROUTE PROCEDURES TERPS

GENERAL What It Offers

Take-off, departure, approach and missed approach obstacle assessment.

Publishes specific climb gradients for obstacle clearance and/or ATC noise abatement requirements.

Based on normal all-engine operations. What It Does Not Offer

Does not consider AFM/FAR take-off and landing limitations.

Does not take into account aircraft performance. (TERPS is not aircraft performance based)

There is no requirement to publish climb gradients for obstacles which may penetrate the TERPS Obstacle Clearance Surface (OCS) provided the obstacle falls under the criteria of low close-in-obstacles.

Does not guarantee one-engine inoperative obstacle clearance AC 120-91. (FAA’s Flight Technologies and Procedure Division AFS-400)

OBSTACLE ANALYSIS

TERPS obstacle planning begins 500 feet either side of runway center-line from the Departure End of the Runway (DER) at ground level (35'AGL prior to TERPS "Change 19"). This initial starting point then splays 15 degrees outward away from centerline. The forming of this horizontal plane then slopes upward at a 40:1 ratio, or 152'/NM (2.5%). This upward sloping plane, now called the Obstacle Clearance Surface (OCS) normally terminates 2NM from the runway, but may extend out to 10nm. The defined area below the OCS is known as the Initial Clearance Area (ICA). The ICA height normally terminates when the aircraft reaches 400’AGL (2NM), know as the Initial Clearance Area End (ICAE). At the ICAE, the OCS plane then surrounds the airport for obstacle assessment to determine if omni-directional departures are authorized. If no obstacle penetrates the OCS a normal TERPS climb gradient is expected which is 200'/NM (3.3%), providing 48’ of obstacle clearance per NM from the DER. Beyond the ICA, TERPS engineers develop procedures based on either a straight-out departure or one with turns involved. The area surveyed is out to 25NM for non-mountainous and 46NM for mountainous airports. Once the aircraft has attained 1,000’ obstacle clearance (non-mountainous) achieved by 21NM, or 2,000’ (mountainous), achieved by 41NM, the assessment area ends as the aircraft altitude meets the minimum enroute obstacle clearance criteria. Normally, if no obstacle penetrates the OCS, standard take-off minimums are published (1SM for 1 and 2 eng. 1/2SM for 3 and 4 eng. aircraft) and unrestricted omni-directional departures are authorized. TERPS criterion expects the aircraft to climb a minimum of 200’/NM to the published nearby MOCA or MEA. Obstacle Penetrating the OCS An obstacle penetrating the OCS may require a higher than normal TERP climb gradient, an avoidance maneuver or possibly a combination of the two. If the obstacle can be avoided with a higher climb gradient, TERPS will publish the required gradient to a specified height to clear the obstacle and thereafter assume the aircraft will continue the climb at a

minimum of 200’/NM to the published MOCA or MEA. For aircraft unable to meet the higher climb gradient a ceiling and visibility is published which allows for a climb in visual conditions. TERPS engineers develop departure and arrival routes, procedures and minimums based on obstacle clearance “guidelines”, with no set hard and fast rules which they must follow. They can go well beyond the set minimums and provide additional clearance where they deem necessary. Depending on obstacles and/or terrain, a design engineer can develop climb gradients and/or splays that are only specific to that airport.

TYPES OF OBSTACLES LOW CLOSE-IN-OBSTACLES

A low close-in-obstacle is defined as an obstruction located within 1SM from the DER which may penetrate the OCS by up to 35’. TERPS will publish the type, location and height but not a climb gradient to clear the obstacle. It is the responsibility of the pilot to see, maneuver and avoid low close-in-obstacles. TERPS considers the aircraft will clear the runway end by 35’ and continue on a 200'/NM climb gradient, therefore clearing the obstacle in question. This may sound somewhat acceptable, yet not the safest practice. If one should consider using "Wet" aircraft performance, the DER crossing height could be as low as 15'. TERPS procedures verses aircraft performance have no relation to one another.

Important Note: In order to compare AFM performance (Reference Zero) to TERPS calculations (DER) equally, we must use the same origin point. This is accomplished by considering the runway length is equal to the take-off distance, such as a balanced field. This places Reference Zero at the DER.

Following is a TERPS/APG comparison example of a close-in-obstacle. Chicago’s Midway (KMDW)

Midway airport publishes numerous close-in-obstacles for RWY 4L. One obstacle in particular is a sign 1,912’ from the DER at 88’ in height as highlighted on Jeppesen’s 10-3OB1 textual description. For this example we’ll consider it as the most limiting obstacle on the departure. Note the take-off minimums for RWY 4L from the 10-9A chart, no gradient is published. A normal 200’/NM (3.3%) climb gradient is assumed under TERPS. KMDW was TERP’d prior to Change 19 so the OCS will start at 35’ above the DER instead of runway

elevation. We’ll call this point “reference zero” as discussed earlier, to compare APG and TERPS equally. Starting out with a 2.5% TERPS obstacle gradient (OCS) measured out 1,912’ from the DER the height of the slope is 83’. The obstacle stands at 88’, penetrating the OCS by 5’. Defined as a close-in-obstacle, TERPS does not publish a climb gradient to clear it, hence no mention of a climb gradient on the 10-9A chart. TERPS considers the aircraft will clear the DER by 35' and if the climb continues on a 3.3% gradient the obstacle should be cleared by 10'. Unfortunately, under FAR 25 aircraft certification, there is no requirement to demonstrate a 3.3% gradient. The aircraft only has to demonstrate a 2.4% gradient on take-off to 400'AGL to name at least one of the take-off requirements. We can further complicate the performance issue when we consider "Wet" performance. Wet data resets the “reference 0” crossing height to a minimum of 15'. Therefore, comparing TERPS procedures to aircraft performance is like comparing apples to oranges. The 10-9A publishes a RWY 4L OBSTACLE DP; “Climbing right turn to 2400’ heading 100º before proceeding on course.” The obstacle DP is associated for turns climbing out of 400’AGL and not for the close-in-obstacles. There are several distant obstacles located along the extended centerline of RWY 4L and the obstacle DP provides a heading in order to clear those obstacles. Consulting AFM performance data for this runway I would expect a near MGTW on an ISA day. The runway is 5,507, quite long enough for a heavy weight take-off from any aircraft within the fleet. Without considering obstacles for this departure and merely basing it on field length and FAR 25 climb limit weights you would expect an unrestricted weight takeoff. Without considering close-in-obstacles in this particular case you would be operating at weights above the maximum that ensures sufficient clearance in the event of an engine failure.

What can a runway analysis provide?

As we understand performance and the criteria for clearing obstacles, AFM charts are designed to clear obstacles by a minimum of 35’ using a net gradient climb path. The gross gradient is diminished by 0.8% per FAR 25.115 to yield a net gradient. Remember, the aircraft is climbing on a “gross” gradient, just as you assume using the normal TERP 3.3% gradient. A runway analysis would reference the field length and climb limit charts, as discussed previously, but will now incorporate an obstacle clearance calculation. In the previous example, an analysis would determine a required obstacle net gradient of 4.6%3 for a “dry” takeoff, or 5.64%4 obstacle gradient for a “wet”

takeoff. The engine-out gross gradient would be 0.8% greater. Therefor the aircraft would clear the obstacle by 50’ gross in either case. The idea shows how important it may be to perform an analysis and not only rely on a Field Length or Climb Limit weights, such as derived from the FMS. If close-in-obstacles were not taken into account, and the analysis was instead performed using a normal required TERP 200’/NM (3.3%) gradient, such as using EFB-Pro or Ultra-Nav, your NET gradient would only be 2.5%. Insufficient for obstacle clearance in this case. A limitation of using this type of software if the location of obstacle is not precisely known. 3 Height of aircraft must be 123’AGL “Net” at the obstacle to

be 35’ above the top (88’+35’). Since the climb gradient starts at 35’ the formula is 88’/1912’ = 4.6% Gross height at the obstacle would be .08% higher. (.008x1912’ = 15’) clearing the obstacle now by 50’.

4 Height of aircraft must be 123’AGL “Net” at the obstacle to be 35’ above the top (88’+35’). Since the climb gradient starts lower at 15’, wet runway performance, the height to climb becomes 108’. The formula is now 108’/1912’ = 5.64% Gross height at the obstacle would be .08% higher. (.008x1912’ = 15’) clearing the obstacle by 50’.

OBSTACLES WITHIN 3SM

If an obstacle penetrates the OCS within 3SM (other than low close-in-obstacles), TERPS will:

1. Publish a note on the airport diagram or departure procedure which includes the type of obstacle, location and height.

2. Publish standard take-off minimums but with a required climb gradient to clear the obstacle.

3. Provide weather minimums as in ceiling and visibility to visually clear the obstacle for those aircraft that are unable to maintain the required climb gradient. and/or

4. Develop a textual or graphic route to avoid the obstacle.

OBSTACLES BEYOND 3SM

If an obstacle penetrates the OCS beyond 3SM TERP’s will:

1. Publish standard take-off minimums but with a required climb gradient to clear the obstacle.

2. Develop a Visual Climb Over Airport (VCOA) procedure for aircraft that are unable to meet the climb gradient, and/or

3. Develop a textual or graphic route to avoid the obstacle.

Following is an example of how TERPS publishes different departures for an airport having both near and distant obstacles. Corvallis, OR (KCVO)

As well as having close-in-obstacles, Corvallis publishes a SID, an obstacle DP, and a VCOA procedure. Planning the CVO1 SID from RWY 17 or 35 alleviates the requirement for the higher published DP climb requirement of 290’/NM. The CVO1 is TERP’d at a standard climb gradient of 200’/NM. The remaining two options for this departure is an obstacle DP requiring a higher climb gradient, 290’/NM to 3100MSL, or the VCOA procedure which requires a minimum of a 1700' ceiling and 3SM visibility. For a low visibility take-off, the CVO1 or the Obstacle DP requires maneuvering to maintain adequate obstruction clearance all while maintaining a TERPS minimum climb gradient. APG does not publish runway data for the obstacle DP or the CVO1 SID. APG only publishes straight-out departure runway performance data. Planning considerations should consider a limited takeoff weight as well as a defined departure course in the event of an engine failure. Using APG straight-out takeoff weights may not provide obstruction clearance if planning on using the DP procedure or the CVO1 SID. One recommendation to consider is to depart straight-out and climb to the obstacle DP altitude of 3400’ before commencing a turn.

MISSED APPROACH, REJECTED AND BALKED LANDINGS

TERPS accounts for obstacle clearance during the approach and missed approach phase much in the same way it does for take-off and departure. TERPS assumes the aircraft will climb a minimum of 200’NM (3.3%) starting from the missed approach point. Once the aircraft descends below the DA/MDA and the pilot executes a rejected or balked landing, adequate obstruction clearance has been compromised. A careful analysis of the missed approach area and any published gradients should be reviewed in the event a rejected landing might be anticipated especially conducting a single engine approach. As per certification, one of the three criteria for maximum “climb limit” take-off weight is the aircraft must be capable of meeting the Approach and Landing Climb requirement within 15 minutes after take-off. The approach climb requirement assumes an engine-out gross gradient of 2.1% at approach flap setting and GA power. We’ll use the GIV as an example. If planning a Flaps10 take-off for climb performance but then deciding on an emergency return due to an engine failure, takeoff performance is based on conducting a possible missed approach at the departure airport using a Flaps20 setting. Therefore, the WAT limit weight may be more restrictive than the runway or obstacle limit weight for take-off. The same will apply for the Global where the take-off may be conducted with Slats, Slats/Flaps6 or Slats/Flaps16, but the approach climb limit weight will be predicated on a missed approach conducted at Slats/Flaps6.

OBSTACLE CLEARANCE FOR AIR CARRIERS

GENERAL Air Carrier regulations (121 and 135) publish specific obstacle clearances for take-off. The minimum was set to 200’ laterally within the airport boundary and 300’ beyond the airport boundary. These lateral distances had to be specific for each aircraft, i.e. based on the aircraft’s wing-span. Of course these regulations were written when the DC-3 was the common carrier of air transportation in the 1940’s. Today’s environment it is much too narrow for the speeds in which we operate at today. To help air carrier operators of today transit from the takeoff to the enroute environment it took over 30 years, where in 1976 Advisory Circular 120-91 was published and then updated in 2006 by the FAA. It is this circular that APG uses to determine obstacle clearances for take-off and landing. As an advisory document, it is mandatory for Air Carriers to adhere to it and highly advisable for Private Operators to follow suit.

AC120-91

This advisory circular was developed to fill the void between the limited air carrier regulations and what TERPS did not address for safe engine-out obstacle clearance. The advisory circular picks up where 121/135 obstacle clearance requirements left off. Starting from the 300’ lateral clearance beyond the airport boundary it continues out to 4,800’ and then begins a splay of 16:1. The 16:1 splay continues out until a horizontal clearance is 2000’ on each side of the departure route. If a turn is required on the departure the horizontal clearance increases to 3000’ for the turn. A degradation of climb is also factored into the aircraft’s climb performance for climbing bank turns, which TERPS does not address.

Vertical obstacle clearance will be based on the aircraft’s gross performance certification flight path reduced by 0.8% for two engine aircraft. This reduced path, known as a NET flight path, will be used as the minimum flight path to clear obstacles.

TERPS vs. APG The one question asked quit often concerning APG. How does APG provide greater obstacle clearance as well as allow a heavier takeoff weight in some cases? Geometry, Geography. 1. Geometry: More often than not we depart

runways much longer than balanced field length distances. This moves “Reference Zero” closer to the “Brake-Release-Point” or further away from the DER. The result is a shallower or lower percent climb gradient required to clear the obstacle, hence additional lift capacity. TERP’s assumes an aircraft will maintain, at minimum, 3.3% gradient for obstacle clearance. If APG determines that no obstacles are present along the departure path a max climb-limit weight may be published considering runway length is sufficient.

2. Geography: TERP’s obstacle assessment is Area based where as AC120-91 is Flight Track based. TERP’s considers all obstacles within a predefined area, not necessarily the departure path of the aircraft. AC120-91 specifies obstacle clearance criteria based on the aircraft’s departure track, which includes loss of performance for maneuvering as well as actual flight track based on turn radii, which is predicated on weight and speed.

OTHER ISSUES TO CONSIDER § The FMS defaults to the published runway

length, usually TORA. Therefore, the FMS treats TORA equal to ASDA. There are runways where the published ASDA is shorter than its TORA. The example below will show how the FMS as well a Jeppesen chart may have misleading data without checking all available information. Florida’s Naples Municipal Airport (KAPF).

§ Most information shown on a Jeppesen airport diagram is also published in the AF/D. Comparing Jeppesen’s 10-9 airport diagram to the AF/D you’ll notice the AF/D publishes RWY 14/32 ASDA shorter from what Jeppesen shows

as usable runway. Jeppesen does not show Runway 14/32 distances are limited for Takeoff. One could assume that RWY14/32 has 5000’ available for take-off, when in fact the published ASDA is shorter on both runways, which becomes a limiting factor when computing take-off performance. NOTE: By design, if an airport chooses to use federal money from the Airport Improvement Act Fund, one of the many requirements for runway improvement is that the airport must adhere to Advisory Circular 150/5300-13. The AC stipulates that a specific clear-zone or obstacle free area must be addressed for each runway. Naples, in this case, was unable to meet this requirement. The result would affect the accelerate-stop distance. This required Naples to limit ASDA distances for both 14 and 32. This important bit of information can be found in the AF/D but unfortunately not on the Jeppesen chart. Jeppesen is somewhat misleading. The reduction in runway lengths Jeppesen shows by the ball notes only references distances that are unavailable for landing distance computations.

§ Jeppesen and the AF/D will also show displaced thresholds where the FMS does not. The FMS defaults to TORA. RWY 14/32 limits LDA to 4420’. APG calculations take this data into account.

§ APG will take into account the degradation in climb performance during bank turns. TERP’s does not. TERP’s is simply a rise/run calculation with no concept of actual aircraft performance.

§ Under TERP’s, an ATC assigned heading, after radar contact is established, may be used for obstacle clearance in some cases. If the heading is not followed after an engine failure the flight path is now compromised for adequate obstacle clearance. Under an APG analysis, if a SID does not exist, APG will publish an initial departure heading and best course of action to follow. An APG analysis will also publish a takeoff limit weight for a continued straight-out departure valid for 30NM as an alternative to maneuvering.

§ Another drawback with TERPS is when low close-in-obstacles are present. Visibility criterion is measured from the DER and not from the take-off position. During a low visibility take-off, you may not see the end of the runway nor the obstacles just beyond the DER.

§ Another caution to be aware of are SID’s using “climb-to-altitudes”. These so called “floating waypoints” remain in front of the aircraft until the condition is met. Performing a runway analysis might remove these waypoints and replace them with a fly-over waypoint. APG will define a fly-over by providing a Place/Bearing/Distance from a known fix. White Plains SID for example uses climb-to-altitudes, for 16 and 34. APG removes these “floating waypoints” and replaces them with P/B/D waypoints using CMK VOR.

§ Switching from dry to wet performance data can make an obstacle that was not limiting to one that is now limiting. Using wet data effectively raises the height of all obstacles by 20’.

§ Temperature change has a direct relation on which obstacle is the most limiting. As temperature changes so may the most limiting obstacle’s location along the flight path. As an example, an obstacle that is limiting within the second segment at one temperature could now

be an obstacle located within the third or forth segment at a different temperature.

UNDERSTANDING APG ANALYSIS

GENERAL After running your APG analysis the important

items to consider are: § Adjusting your limit weight according to the

benefits/penalties set at the bottom of the range table if referencing APG’s Atlas legacy tab data performance. If using the AGP’s NextGen performance information all variables have been accounted for.

§ Identifying your level-off height where aircraft clean-up and acceleration will take place.

§ If using wet/contaminated data, ensure you are using the correct V1 speed which may not be the FMS derived speed. A manual V-speed entry may be required.

§ If APG publishes a defined obstacle avoidance procedure ensure it matches the SID you are using. If not, you will need to plan accordingly.

§ If APG issues an immediate turn on departure this turn is to be started over the departure end of the runway at a bank angle not to exceed 15 degrees.

§ I using the Atlas tab data compare the climb limit weight to the obstacle limit weight to determine max take-off weight.

APG DATA

“0” WIND RUNWAY LIMIT WEIGHT An APG analysis for a given runway will promulgate a table showing limited weights for the aforementioned 7 conditions, listed on page 1, based on varying temperatures up to the maximum temperature allowed for that airport elevation. Each weight vs. temperature is a “0” wind, standard atmosphere (29.92) limit weight. Corrections to the runway limit weight may be made for headwind but must be made for tailwind. Non-Standard altimeter corrections to the runway limit weight may be made for a high QNH setting but must be made for a low QNH setting. When running an analysis, other considerations/penalties one must consider is type specific. Flap configuration and wet/contaminated runway conditions must be selected from the performance box settings in order for them to run in the analysis.

GLF4 AIRCRAFT PERFORMANCE GENERAL § Maximum payload is achieved, in most

cases, using a balanced field V1 where obstacle limited take-offs are best using the highest V1 possible.

§ Gulfstream take-off performance is predicated on a “rolling take-off”. Thrust should be set to 1.5 EPR and stabilize for 15 seconds prior to releasing brakes as per the AFM.

§ The FMS performance computer is limited to 5-minute takeoff performance criteria. APG data is from the AFM and takes into account a 10-minute limitation. Crews may have to manually enter take-off speeds for heavy weight, high temperature departures. When setting speeds manually into the Display Controller begin with VSE and work “upward’ to V1.

§ Planning a takeoff weight below the maximum weight for a given temperature, plan on using the V1 associated for the lower weight from the APG table.

GENERAL WET/CONTAMINATED DATA § Gulfstream provides takeoff and landing

wet/contaminated performance data under AFM Supplement OIS-2A Section A (Takeoff and Landing) and/or B (Takeoff only).

§ APG provides wet/contaminated data for take-off only.

§ APG’s depth of contaminate shown in the adjacent screen shot is an “actual” depth.

§ If an APG analysis returns “0” for a limiting take-off weight, the runway environment has failed the conditions required to use the supplement data, or in some cases where V1 has dropped below V1MCG. Examples are: Using OIS Section A data at airport

pressure altitudes above 7000’, or Using OIS Section B data on a down

slope runway.

OIS-2A SECTION A OIS Supplement Section A provides both

wet and contaminated take-off/landing data. The data tables are used with FMS operations by modifying the runway length for take-off or comparing runway length for landing. Section A can only be used if the conditions, which the data is based on, are present. The restrictions are listed in the supplement on page 2. • If using the OIS supplement for take-off

select the appropriate table to modify the runway length as given under the appropriate RSC value. The FMS will automatically re-compute V1 for takeoff and/or recompute a maximum take-off weight. If used for landing, ensure the runway required as per the RSC value, is greater than actual runway length.

• If using APG data for take-off calculations in lieu of manually modifying the runway length, a V1 speed will be provided for that temperature and weight calculation. This V1 speed is then manually entered on the TAKEOFF DATA page.

• APG does not provide wet/contaminated "Landing" runway data for the GIV.

OIS-2A SECTION B Section B provides tab data for a wet take-off

only. Tab data is used in lieu of the FMS derived take-off speeds and dry runway length. Section B can only be used if the conditions, which the data is based on, are present. The restrictions are listed in the supplement on page 12. • If using the supplement tab data, select

the appropriate table for the given conditions. The table will provide both a new V1 speed and new take-off field length. The new V1 speed is manually entered on the TAKEOFF DATA page. Ensure runway length required is within the actual runway length available for take-off.

• If using APG data, enter the V1 speed for the appropriate temperature and weight calculation on the TAKEOFF DATA page.

It is almost futile without a computer program, to adequately use GAC charts for dry, not to mention wet/contaminated runway operations under obstacle climb limited conditions. GAC charts and graphs are initially based on “reference” values. The charts have to be run backward to establish “actual” performance values to use against tab data. It is prudent and otherwise the safest practice to run an APG analysis which takes into account all performance conditions. The following is a screen shot of the GIV takeoff Runway Analysis “Tab Data” selections from the ARINC web site.

MIDWAY 4L DEPARTURE Let’s circle back to the discussion on Midway’s RWY 4L close-in-obstacles. The Midway example was used to show how close-in-obstacles may impact take-off performance. Below is a comparison of G-IV performance weights between AFM TAB Data and APG. DRY Runway OAT 20º - WIND 0/0 - BARO 29.92 - Flaps20 APA 1,000’ Table TAB Data - 72,367lbs (Interpolated) APG Point Performance APG Data- 71,646lbs (Obstacle Limited) WET Runway OAT 20º - WIND 0/0 - BARO 29.92 - Flaps20 APA 1,000’ Table OIS 2A – Section B TAB Data - 68,550lbs (Interpolated) APG Point Performance APG Data - 63,794lbs (Obstacle Limited) You’ll notice APG is less than TAB Data in both cases. In the wet takeoff scenario OIS-2A Section B was used for weight comparison. APG will not run 4L wet data using Section B since it is a downslope runway. APG will only run Section A Tab Data since all conditions must be met to use the data. The idea is only to show that APG can be more limiting in such cases. Note: APG provides a greater selection of contamination methods if selected through “Point Performance” vs. Tab Data “Runway Analysis”.

GL5T AIRCRAFT PERFORMANCE GENERAL § APG shows EPR settings for both Bleed

Closed and Bleed Open configurations. § Global engine out performance uses 10 min

take-off thrust performance. § Global performance does not take credit for

Clearway or Stopway. WET/CONTAMINATED DATA § Both Dry and Wet runway performance

information is computed from a static take-off.

§ An APG analysis can be run for a wet and/or contaminated runway for both take-off and landing.

X-W > 20kts § APG will show a weight penalty for high X-W

conditions. There is no need to add the AFM limitation for distance as APG indirectly does this by reducing the aircraft weight.

The following is a screen shot of the Global takeoff Runway Analysis “Tab Data” selections from the ARINC web site.

MIDWAY 4L DEPARTURE

Below is a comparison of Global performance weights between the FMS and APG. In this case I compare FMS, which is basically TAB Data to APG. DRY OAT 20º - WIND 0/0 - BARO 29.92 Slats/Flaps6 FMS Data - 86,580lbs APG Data - 84,600lbs (Obstacle Limit) WET FMS Data - 86,580lbs (Reduced V1) APG Data - 83,700lbs (Obstacle Limit)

As you can see from this example, as with the Gulfstream, the close-in-obstacles are a limiting factor to take-off weight.

Note: APG provides a greater selection of contamination methods if selected through “Point Performance” vs. Tab Data “Runway Analysis”.

CL604 AIRCRAFT PERFORMANCE GENERAL

§ The Challenger FMS uses Smart-Perf, which provides corrections to take-off distance for varied conditions. An APG analysis can supplement the FMS data especially with the use of climb limited obstacle data.

§ Challenger engine out performance is limited to 5 min take-off thrust.

§ APG shows N1 settings for both Bleed Closed and Bleed Open configurations.

§ Challenger performance does not take credit for Clearway or Stopway.

WET/CONTAMINATED DATA § Dry runway performance information is

computed from a rolling take-off. Wet runway information is computed from a static take-off.

ANTI-SKID INOP § For Anti-Skid inoperative conditions beside a

weight penalty there is also a reduction in V1 required to account for the reduced accelerate-stop distance. For APG Tab Data calculations subtract the penalty speed from the Maximum Allowable Takeoff Weight V1 speed. Compare the Actual Take-off weight V1 to the recomputed Maximum Take-off Weight V1 and use the lower value.

EXTENDED SECOND SEGMENT CLIMB § If the second segment of the takeoff flight

path extends beyond an altitude of 1500’AGL, adjustments need to be made to the takeoff speeds and takeoff weight as limited by takeoff distance, brake energy, and tire speed, as outlined in the AFM Page 06-03-26. Add the V-speed increment to V1, VR and V2 to the takeoff V-Speeds. The limiting takeoff weight, as listed above, will contain the weight adjustments as required.

MIDWAY 4L DEPARTURE

Below is a comparison of Challenger performance weights between the FMS and APG. DRY OAT 20º - WIND 0/0 - BARO 29.92 FMS Dry - 44,700lbs (Rolling T/O) APG Dry - 42,880lbs (Rolling T/O) (Obstacle Limit) WET FMS Wet - 44,100lbs (Static T/O) APG Wet - 42,900lbs (Static T/O) (Obstacle Limit)

As you can also see in this example as compared to the rest of the fleet, the Challenger is also limited due to close-in-obstacles. With APG providing safe clearances for nearby obstacles compared to TERPS, a distant obstacle analysis will provide additional clearance as the aircraft moves further away from the runway on departure. Albeit, a safe and practical way to add a bit more guidance on departures.

The following is a screen shot of the Challenger takeoff Runway Analysis “Tab Data” selections from the ARINC web site.

Note: APG provides a greater selection of contamination methods if selected through “Point Performance” vs. Tab Data “Runway Analysis”.

CLIMB PERFORMANCE Part II (DEUX) INTRODUCTION

This article addresses specifics about Gulfstream and Bombardier climb performance reviewing nuances, interpretation and correct use of performance charts. The first article, “APG Performance”, introduced how APG can help support/supplement a crew’s decision when planning a takeoff from mountainous or obstacle burdened airports. When looking closer at departure planning there are differences between Gulfstream and Bombardier climb performance with regard to the use and interpretation of climb charts. This summary takes a closer look between the two when planning these types of departures. The article is to help accept and support the use of APG performance within the flight department. I’ve generalized to a great extent without getting into the exact specifics to make the article short and concise. If a more detailed discussion/explanation is desired/required, please feel free to discuss.

GULFSTREAM PERFORMANCE Part II Section 5 of the AFM publishes several charts needed to derive a correct take-off climb gradient for obstacle clearance. The charts are labeled: Available Net Gradient Takeoff Second Segment Climb for Flaps10 or Flaps20, and Close and Distant Obstacle Clearance Net Takeoff Flight Path Charts for Flaps10 or Flaps20. The Available Net Gradient chart is a 400’AGL “snap shot” of climb performance. The chart does not compensate for performance loss with climb in altitude. The Close and Distant Obstacle chart are required to compensate for this degradation in climb performance prior to the use of the Available Net Gradient Chart. DETERMINING A CLIMB GRADIENT ACCEPTABLE CHART METHOD First, one must determine the location of the obstacle to correctly identify the degradation in climb performance by first using the Close-In or Distant Obstacle Chart. The “net” result is then used against the Net Gradient Chart to determine the maximum gross takeoff weight. UNACCEPTABLE CHART METHODS A SID climb gradient may be a fair place to start in determining a takeoff weight using the Available Net Gradient Chart, but certainly not the best practice to follow, nor a correct one. If one were to use the gradient of climb required on the SID against the Available Net Gradient Chart, one important factor left out of the equation is degradation in climb performance based on an obstacle’s location. Remember, the Available Net Gradient Chart is a 400’AGL gradient. Since a SID does not publish the controlling obstacle it is near impossible to determine the performance gradient required or what your aircraft’s climb gradient is going to be other than at 400’AGL. Unless the obstacle’s location and height is known the “Available Net Gradient" chart does not provide the best answer for determining your climb gradient. Even with two obstacles having the same gradient of climb but at different height and distances the loss factor will be different, yielding different gradients resulting in different take-off weights. Unless you know where the obstacles are you have no way of determining the minimum climb gradient. APG performance does not reference FAA published SIDs but instead derives a safe climb gradient based upon the obstacles along the departure path.

Example An obstacle located 34,000’ (5.6NM) from reference zero stands at 1200’AGL. The “actual” gradient of the obstacle, height/distance, is 3.5%. The Flaps20 Distant Obstacle Chart average climb gradient is about 3.8%. This value is now used to enter the Available Net Gradient Chart to determine the maximum take-off weight. Let’s use this same obstacle as a charted SID. TERPS would publish this as a 4.3% climb gradient to 1,200AGL. Reducing this by 0.8% as taught in training, or using third party programs (Ultra-Nav, EFB Pro), would result in a 3.5% gradient used instead of the correct 3.8% needed. A 0.3% difference is considerable when accounting for higher density altitude, temperature and aircraft weight which could result in a several a thousand pound difference.

BOMBARDIER PERFORMANCE Part Deux Global / Challenger performance charts are published under Chapter 6 Section 4 of the respective AFM. Bombardier uses a different methodology in charting technique compared to Gulfstream. Bombardier charts are labeled: Obstacle Clearance Reference Climb Gradient for Slats, Flaps6 and Flaps16, for the Global or in the Challenger case Flaps20. and, Net Take-off Flight Path Charts for Close and Distance Obstacles. The differences between Bombardier and Gulfstream: The Close and Distant Net Take-off Flight Path

charts do not factor in a climb gradient loss. It is strictly an algebraic gradient of height/distance. Hence, these charts can be used for any flap or bleed configuration. Also, these charts allow a user to evaluate different level-off heights as a function of the take-off power time-limit.

The Obstacle Clearance Reference Climb Gradient chart(s) is/are used to factor in the gradient loss with climb. This is just the opposite approach as used by Gulfstream.

To determine a required gradient a user may go directly to the Reference Climb Gradient Chart and if the correct level off height is known, as with an obstacle height or SID climb requirement, determine a climb gradient required. The challenge comes when it is required to correct V1 and the take-off field length based on factors such bleed configuration and wet runway operations. Once again APG performance data shows the penalties one must account for under differing circumstances alleviating the necessity to refer to the QRH tab data for corrections.

PERFORMANCE DURING FINAL SEGMENT CLIMBS If we extend the take-off profile to include a third and final segment as required for obstacle clearance the margin of clearance increases to that compared to a second segment climb profile. Final segment climb profiles, as per FAR 25, require the gradient of climb to be reduced by 1.1%, compared to that for second segment climbs which is only 0.8%, providing a safer margin of climb with regard to distant obstacles with either Gulfstream or Bombardier performance.

SUMMARY Considering all the advantages of using APG other than just obstacle clearance includes such benefits as field length limits, climb weight limits, brake energy limits, tire speed limits, wet runway limits, corrections to weight for bleed configuration, wind, QNH, and taking into account inoperative components such reversers, anti-skid, auto-spoilers all point to using more reliable data leading to safer aircraft operations.