Performance and Flight Planning - CFM Ch. 5,6 Flashcards
What performance charts are in Chapter 5 of the CFM?
- Wind and Altitude Conversion
- Altimeter Setting to Station Pressure
- Geometric Height to Pressure Height (Indicated to True for Cold Temps)
- Thrust Setting Tables (N1 for T/O-1, N1 for T/O-2, N1 for GA)
- Flexible Temperature Determination Tables
- Simplified Takeoff Analysis Tables
- Takeoff Speeds
- Final Segment Speed
- Stab Trim Setting for Takeoff
- Climb Gradient – All Engines Operating
- Overload Operations (Based on ACN and PCN)
- Approach and Landing Speeds (Vref, Vac, Vfs)
- Flap Maneuvering Speeds (Different from Vspeeds, these are the bug speeds example: Flaps 1, bug 210)
- Approach Climb Gradient
- Unfactored Landing Distance
- Landing Distance Correction Factor
- Flap (Slat) Fail
- Operational Landing Distance
- Quick Turn Around Weight Tables (when the brake temp indication is not working)
- CAT II Operation
What is assumed temperature thrust reduction?
In many situations, the airplane takes off at weights lower than the maximum permissible Takeoff weight. In consequence, it is possible to continue complying with performance limitations using a decreased engine thrust adapted to the actual weight. This is called assumed temperature reduced thrust method.
Certification authorities permit the use of up to 25% of Takeoff thrust reduction for operation with assumed temperature reduced thrust. FLEX
Can FLEX be used when the actual weight is higher than the maximum takeoff weight for the actual temperature?
No. Utilization of Assumed Temperature Reduced Thrust
Assumed temperature reduced thrust method can only be used when the actual weight is lower than the maximum permissible Takeoff weight for the actual temperature.
What are the limitations of FLEX takeoffs?
Maximum Assumed Temperature (MaxAT) (25% reduction). Refer to Maximum Assumed Temperature Table.
Assumed temperature reduced thrust is not allowed when runway is contaminated with water, ice, slush or snow.
The operator shall at regular intervals check the maximum thrust in order to detect any possible engine deterioration, unless the operators has an adequate engine performance monitoring program.
When should FLEX be used?
Assumed temperature reduced thrust should be used whenever possible in order to save engine life.
Always use the flaps configuration, that provides the greatest maximum Takeoff weight in order to maximize thrust reduction.
What is the Maximum Assumed Temperature Table?
The Maximum Assumed Temperature Table, which is presented as a function of OAT and pressure altitude. This table ensures that the assumed temperature does not result in a thrust reduction of more than 25%.
What is the Minimum Assumed Temperature Table?
The Minimum Assumed Temperature Table, which is presented as a function of the pressure altitude. This table ensures that the assumed temperature is greater than the engine flat rated temperature.
What is the N1% Adjustment for Temperature Difference Table?
The N1% Adjustment For Temperature Difference Table, which presents the N1 correction based on the assumed temperature and OAT.
Using the tables in CFM Ch. 5:
- Determine if a FLEX takeoff can be performed.
- Determine the reduced N1%
- Determine the FLEX takeoff speeds
5.8.2 Flexible Temperature Determination
- Verify if actual weight is lower than or equal to the maximum takeoff weight in Takeoff Analysis for correspondent OAT and wind.
- Enter with actual weight and actual wind on Takeoff Analysis and find the correspondent temperature (T).
- Enter with pressure altitude and temperature in Maximum Assumed Temperature table and find Maximum Assumed Temperature value (AT).
- Compart T and MaxAT and choose the lower value as Assumed Temperature value (AT).
- Enter with pressure altitude in Minimum Assumed Temperature table and find Minimum Assumed Temperature (MinAT).
6a. If AT is lower than MinAT: No Flexible takeoff is possible, use maximum thrust
b. If AT is higher than MinAT: Take this temperaure (AT) as Assumed Temperature.
(Note AT is not limited by the MinAT table when it is determined via performance software or airplane system)
N1% for Flexible Takeoff
- Enter with AT and pressure altitude in N1 for T/O-X mode and find out N1 reference (N1ref).
- Enter with the difference between AT and OAT in N1 adjustment for temperature difference table and find out N1corr.
- Reduced N1% is: N1red = N1ref - N1corr
5.8.3 Takeoff Speeds
- Using Runway Analysis, enter with the Actual Takeoff Weight in the reported wind column to find out V1, VR, V2.
- Using Minimum V1 and VR tables find out V1min and VRmin.
3a. If V1 and VR are higher than V1min and VRmin, use takeoff speeds found in step 1.
b. If V1 and VR are lower than V1min and VRmin use the Runway Analysis and find out in what Temperature V1 and VR are equal or higher than V1min and VRmin. Determine again N1% and use this V1, VR, and V2 of previous step as takeoff speeds.
What are the Simplified Takeoff Analysis tables? What are the conditions? What are the limitation factors? Determine the takeoff analysis for a scenario in CFM Ch.5
Simplified Takeoff Analysis tables are presented for a set of pressure altitudes, temperatures and runway lengths for the conditions below:
- Dry runway.
- Zero wind.
- Zero slope.
- No clearway.
- No stopway.
- Obstacles are not considered.
- Maximum manual braking.
- ECS and ATTCS ON.
- Balanced V1.
- Landing flap 5.
B. The following limitation factors and codes were considered in the calculation of these tables:
- R – Runway Length.
- W – WAT (Climb).
- B – Brake energy.
- S – Structural.
- A – Approach Climb.
- SF – Final Segment.
- P – Tire speed.
- L - Maximum Lift-off Speed.
The Maximum Structural Takeoff Weight defined in this manual must be checked.
C. The number preceding any of the letter designators listed above is the limiting Takeoff weight for the runway length denoted at the top of the associated column. Beneath that limiting Takeoff weight, is the associated V1/VR/V2 for the conditions of temperature and runway length used to enter the table.
What are the Takeoff Speed tables? What are the conditions?
The following tables present V1, VR and V2 for balanced runway and fixed V2/VS ratio. The tables have been generated with the settings below: 1. Dry runway. 2. Zero wind. 3. Zero slope. 4. Balanced V1. 5. Minimum V2/VS. 6. Maximum manual braking. 7. ATTCS ON. 8. Anti-ice ON/OFF. 9. ECS ON/OFF.
How is the F-Bug algorithm designed?
During flap retraction, the next flap setting should be selected when the F-Bug is reached.
The F-Bug calculation algorithm is designed so as to meet minimum safe margins to VFE and Shaker Speed. A minimum margin of 20% above the stall speed is set for the next flap.
What are the Climb Gradient - All Engines Operating tables? What are the conditions?
The climb gradient tables show the climb gradients in percentage and in ft/NM for several weights, temperatures and pressure altitudes. These tables are published in the following configurations: A. Gradients for Takeoff Thrust 1. The gradients were obtained for: a. A speed equal to V2 + 10 KIAS. b. FLAP 2. c. V2/VS ratio equal to the minimum of the range. d. Anti-Ice OFF. e. ECS ON. f. Landing Gear Up. g. Wings Leveled. h. Temperatures in Celsius Degrees. 2. Corrections in the climb gradient for Anti-Ice ON and Flaps 4 are also provided in the footer of each table.
B. Gradients for Climb Thrust
- The gradients were obtained for:
a. A Speed equal to VFS KIAS and 250 KIAS.
b. FLAP UP.
c. CLB-1 Thrust Rating.
d. Anti-Ice OFF.
e. ECS ON.
f. Landing Gear Up.
g. Wings Leveled.
h. Temperatures in ISA Deviation. - Corrections in the climb gradient for Anti-Ice ON and CLB-2 thrust rating are also provided in the footer of each table.
What information is in the supplementary takeoff information in CFM Ch. 5?
Turn Analysis (obstacles)
Equivalent Straight Flight Path Determination
ACN Aircraft Classification Number
PCN Pavement Classification Number
What is the PCN Pavement Classification Number?
The Pavement Classification Number (PCN) reported shall indicate that an airplane with ACN equal to or less than the reported PCN can operate on that pavement.
What are Flap Maneuvering Speeds in general? What are the actual speeds?
The Flap Maneuvering Speeds provide at least 1.3 g margin over stick shaker speed, which is equivalent to a shaker-free Bank Angle of 40°. These speeds ensure such margin for all weights up to the Maximum Landing Weight, with or without ice accretion.
The speeds above may be used as reference for flaps extension and maneuvering. For flaps retraction refer to “Flap Retraction Speed Schedule” presented in the Takeoff section of this manual.
The Green Dot on the PFD provides at least 1.3 g margin over stick shaker speed adjusted for the current airplane weight, thus it can also be used as the Flap Maneuvering Speed. The Green Dot also accounts for ice accretion.
See the table for actual speeds (Flaps 1 bug 210, Flaps 2 bug 180…)
What is the Approach Climb Gradient table? What are the conditions?
A. The Approach Climb Gradient tables show the gradients as function of temperature (°C) and weight (lb).\
B. The associated conditions are:
- CAT I Operation.
- Approach Flaps: 2 or 4.
- GearUP.
- Anti-Ice OFF without Ice Accretion or Wing and Engine Anti-ice ON with Ice Accretion.
- ECS OFF.
- One Engine Inoperative.
Unfactored Landing Distance
Unfactored Landing Distance is the actual distance to land the airplane on a zero slope, ISA temperature, dry runway, from a point 50 ft above runway threshold at VREF, using only the brakes and spoilers as deceleration devices (i.e., no engine reverse thrust is used).
Determine the Unfactored Landing Distance in a scenario using the tables in CFM Ch. 5 How should the landing distance be calculated normally? In an emergency?
The Unfactored Landing Distances provided are valid for anti-ice ON and OFF.
A. Normal Operation
- The required Landing distance for dispatch is the Unfactored Landing Distance increased by 66.7% for dry runway, or 91.7% for wet runway.
- For obtaining the DRY runway factored distance, multiply Unfactored Landing Distance by 1.667.
- For obtaining the WET runway factored distance, multiply Unfactored Landing Distance by 1.917.
B. Emergency/Abnormal Operation
1. Landing Distance Correction Factor – Dry Runways
a. The Actual Landing Distance is equal to the Unfactored Landing Distance for flaps FULL multiplied by the associated Landing distance factor for DRY runways.
b. The DRY + OVSP corresponds to the factor associated to a 10 kt overspeed (above the non-normal VREF) on a dry runway.
2. Landing Distance Correction Factor – Wet Runways
a. The WET + OVSP corresponds to the factor associated to a 10 kt overspeed (above the non-normal VREF) on a wet runway.
b. To calculate the Actual Landing Distance on a WET runway, the pilot must do the steps below:
1) Recognize the system malfunction.
2) Find the Unfactored Landing Distance (ULD) for Flaps Full in QRH, considering the airplane type, altitude, Landing weight and ice accretion condition.
3) Find the multiplier factor value (K) on the table with Landing Distance Correction Factors and multiply the obtained values of (ULD) and (K).
4) In the same line of table with Landing Distance Correction
Factors, find the value (B).
5) Subtract (B) from the result of step c above. This is the Actual Landing Distance (ALD) to safely land the airplane on wet runways condition.
ALD = (ULD x K) - B
The calculated value is the actual distance to safely land the airplane, but no distance margins are included. The distance margin available is the difference between the runway length and the calculated value.
Shortest Unfactored Landing Distance in the charts = 1662’
So the shortest required landing distance is x1.667 dry = 2,771’
Longest Unfactored Landing Distance in the charts = 5,606’
So the longest required landing distance is x1.917 wet = 10,747’
Max Manual Braking. Emergency situations not accounted for.
What are the Operational Landing tables? Determine the operational landing distance given a scenario using CFM Ch. 5
The Operational Landing Tables are intended for in-flight assessment, not for dispatch.
A. The Operational Landing Distance Tables contained herein are based on FAA AC 25.32. The data do not include any multiplication factor or additional safety margin.
B. The distances are obtained from 50 ft above threshold until full airplane stop and consider credit for all thrust reversers. Local operational regulations may require an additional factor to these distances. Emergency/abnormal multiplication factors were not analyzed for contaminated runways. For Emergency/Abnormal Operation, refer to “Unfactored Landing Distance” section in this chapter.
C. In order to make the in-flight assessment if the runway condition is reported, the Runway Condition Assessment Matrix (RCAM) is used. It offers a correlation between runway condition and the pilot report (PIREP). The maximum recommended crosswinds are also presented in relation to each PIREP. Gust effects are not included and do not affect the recommended crosswind values.
D. The Operational Landing Tables must be entered with runway braking action, Landing flaps, ice condition, autobrakes configuration, current Landing weight, Landing field pressure altitude, temperature, wind, slope, airplane overspeed above VREF and thrust reversers.
E. As an example, assume the following condition for the EMBRAER 175:
1. Assume the following condition:
a. Reported braking action: Good to Medium
b. No ice conditions
c. Flaps: 5
d. Autobrakes: OFF (Max Manual)
e. Landing weight: 70000 lb
f. Airport Pressure Altitude: 3000 ft
g. ISA -25°C
h. Wind: 10 kt headwind
i. Slope: 0%
j. VREF + 5 kt at threshold
k. All thrust reversers use
2. In flaps 5 and no ice accretion. In the MAX MANUAL braking line, find the reference weight and distance in the first column. These values are:
a. REF DIST = 4820 ft
b. Reference weight = 72000 lb
3. Next correction regards the airplane actual Landing weight. Take the difference from the reference weight to the actual weight. In this case, the actual Landing weight is 2000 lb below the reference. The correction is - 49 ft for each 1000 lb below the reference correction:
a. Weight correction = 4820 - (49 x 2) = 4722 ft
4. Next correction is pressure altitude. The value is 138 ft for each 1000 ft above Sea Level. Apply the correction for 3000 ft:
a. Altitude correction = 4722 + (138 x 3) = 5136 ft
5. Next correction is temperature. The value is -48 ft for each 5°C below ISA, apply the correction for ISA -25°C:
a. Temperature correction = 5136 - [(25 ÷ 5) x 48] = 4896 ft
6 Next correction is wind. The value is -116 ft for each 5 kt headwind, apply the correction for 10 kt headwind:
a. Wind correction = 4896 - [(10 ÷ 5) x 116] = 4664 ft
7 Next correction would be the slope. Since the slope is 0%, there is no correction. We go directly to the VREF correction. Considering an overspeed correction of 394 ft for each 5 kt above VREF:
a. Overspeed correction = 4664 + 394 = 5058 ft
8 The last correction regards the thrust reverser. Since both reversers are used, no correction is necessary.
9 The required Landing distance is then 5058 ft.
In case the airplane lands above the Maximum Landing Weight (MLW), the overweight correction in the footer is necessary. Proceed as follows: Take the reference Landing distance in the first column; skip the weight correction and do all other corrections. At last, apply the footer overweight correction.