23

There are basically 3 limits that the engine faces, temperature (maximum turbine entry temperature or maximum compressor exit temperature), pressure (maximum compressor exit pressure) and stress (maximum stress in the blades as a result of spool speed). Varying the OAT for a specific engine design will hit one of these limits. When the OAT increases, the ...


22

Takeoff power is almost never maximum engine power. Maximum power affects engine life as it brings significant wear to the engine. IIRC, if max power is used on takeoff, the crew must log an entry in the logbook to notify maintenance. Turbo-fans produce a lot of power. If you require max power to takeoff, you better double-check your numbers, or you're ...


17

What is the difference between clearway and stopway? The definitions linked in the question for a clearway and stopway are fairly adequate. AC 150/5300-13A Airport Design Clearway - is an area extending beyond the runway end available for completion of the takeoff operation of turbine-powered aircraft. A clearway increases the allowable aircraft operating ...


16

Is the takeoff power always maximum? No, unless it is required. Disadvantages for using full power on takeoff is higher fuel consumption, noise, and engine wear. Instead, takeoff performance is calculated and the appropriate thrust setting is used. You need lower setting if: runway is long no obstacle to clear during climb runway is dry temperature is ...


12

Follow the arrows in the graph. You start with the gross weight on the right X-axis and move straight upward until you intersect the correct field elevation. In the graph the line starts at 58,000 lbs and moves up to a field elevation of approx. 1700 ft. From there move left into the left side of the graph. There, the X-axis is the effective headwind speed....


12

What you see is called a flat rated engine. It means the maximum thrust from the engine is constant below the flat rated temperature (usually 30°C). Above that temperature, thrust will decrease due to the EGT (exhaust gas temperature) limit. In order to achieve a constant thrust at lower temperatures, the N1 needs to be decreased accordingly. (CFM56-5A ...


11

We round up for safety, so assume PRESS ALT=1000' and TEMP=30° Celsius, we would have a ground roll of 890' and a takeoff distance of 1645', right? Good thinking, but no. Refer to the Pilot's Handbook of Aeronautical Knowledge, Chapter 10. You want page 10-3 specifically. When the altimeter setting is 29.92, the pressure altitude is the same as the ...


10

Short Answer Getting to grips with Aircraft Performance and Calibrated Airspeed are two good places to start! The short answer: From TAS to IAS $IAS=f(TAS)$: $$IAS = a_0 \sqrt{5\left[\left(\frac{\frac{1}{2} \rho {TAS}^2}{P_0} + 1 \right)^{\frac{2}{7}}-1\right]} + K_i $$ From IAS to TAS $TAS=f(IAS)$: $$TAS = \sqrt{\frac{2 P_0}{\rho}\left[\left( \frac{ ...


9

I found a different number for $C_L$, please check your calculation: $C_L=\frac{2 m g}{\rho V^2 S}$ substitute: $ m = 50000 \textrm{ kg}\\ g = 9.81 \textrm{ m}/\textrm{s}^2\\ V = 462 \textrm{ KTAS} = 237.67\textrm{ m/s}\\ S = 122.6 \textrm{ m}^2\\ \rho = 0.475 \textrm{ kg}/\textrm{m}^3 $ This will give: $C_L = 0.298$ Note that this lift coefficient is ...


9

The takeoff and landing speeds of aircraft can usually be found in the performance section of the aircraft light manual. They are not fixed and vary over a wide range depending on various factors like, temperature, density altitude weight etc. The table below gives the takeoff speeds for Learjet 45, taken from Learjet 45 AFM: Learjet 45 Takeoff speeds; ...


9

You are not wrong, it is more efficient to accelerate a large mass by a little than a small mass by a lot. This is due to momentum being linear with speed and mass, while energy is linear with mass but quadratic with speed, so the same momentum can be obtained more efficiently by slowly pushing a large amount of air, e.g. with a large propeller. The ...


8

Note that this answer was given to the original question, Do pilots need to use trigonometry as part of their routine job? If so, when is it most used and for what? The question was subsequently edited, after this answer was accepted. Much of the information provided in this answer does not now apply directly to the current question, but it does serve to ...


8

Course and heading are not the same. Course is the direction of your path over the ground. Heading is the direction you are pointed (and the direction you would travel through a still airmass). In your second site you entered 120 as a heading, not a course. Correct that and you get the same figures as the final site. You're doing the same thing in your ...


7

You need to read such graphs strictly from left to right. Each new panel adds the influence of another parameter, and when you are done, the result is corrected for altitude, take-off weight, wind and obstacle height. Except for the leftmost panel, the groups of lines only help you to find the correct slope and do not represent a certain altitude. You start ...


7

Fuel bias is as you described it. As the engine ages, it burns more fuel than a brand new one. The fuel flow (and drag) corrections are entered into the FMS. This would allow the FMS calculated quantity not to disagree with the tanks totalizer. The figures are based off previous flights and engine tests. Maintenance personnel can refine the database by ...


7

The equations of motion are the easy part. In essence, you look at all forces affecting the aircraft (lift, thrust, drag, weight) and balance them with proper control settings (elevator, throttle) and accelerations (if thrust > drag, the forward acceleration is (thrust - drag)/mass). This you repeat over and over, one timestep at a time. The next timestep ...


6

The glide ratio for a given angle of attack is the ratio of lift to drag. Both of these are proportional to the respective coefficients (with a proportionality constant of $\frac12\rho v^2A$), so the glide ratio is simply $c_{\mathrm L}/c_{\mathrm D}$. Practically, what you're looking for may be the maximal glide ratio. Finding the global maximum of $$\frac{...


6

Using the Mach number definition $M=\frac{V}{\sqrt{\gamma RT}}$, the ideal gas equation $p=\rho RT$ and the atmospheric pressure ratio $\delta=\frac{p}{p_0}$: $$ \frac{1}{2} \rho V^2 = \frac{1}{2} \rho \cdot \gamma RT \frac{V^2}{\gamma RT} = \frac{1}{2} \gamma p \cdot M^2 = \frac{\gamma \cdot p_0}{2} \cdot \delta \cdot M^2 $$ With $p_0=2116.2 \text{lbs}/\...


6

From mns' answer $$DescentRate = 0.0524 \cdot GroundSpeed$$ But the Ground speed is in [nm/h], and the descent rate is in ft/min. So we have $$DescentRate \left[\frac{ft}{min}\right] = 0.0524 \cdot GroundSpeed\left[\frac{NM}{h}\right] $$ With $6076.12~ft~per~NM$ (yay for imperial units) and $60~minutes~per~h$ we get a conversion factor: $$ \left[\frac{...


6

Just take a look at the geometry, the ground speed and descent rate vectors are perpendicular to each other. If $\gamma$ is the descent angle, the formula you are interested in is: $$tan(\gamma) = \frac{DescentRate}{GroundSpeed}$$ For $\gamma = 3°$ $$DescentRate = 0.0524 \cdot GroundSpeed$$ Obviously, you have to convert the result to the desired units.


6

I have analyzed this information before, and this is what the chart looks like with one line for each weight category if you convert the temperature and pressure altitudes to density altitudes and then chart that vs. the takeoff distance: You can see that I have drawn a sort of best-fit line for this information. I did not add humidity as a factor because ...


6

With the set of parameters available to you, you cannot do this. If you have the actual track instead of the desired track, you will be able to calculate the wind. The simplest way to do this is using vector math. There are three vectors to consider: ground speed vector $\vec{V_{gs}}$ air speed vector $\vec{V_{as}} $ wind speed vector $\vec{V_{ws}} $...


6

Each propeller blade is a wing in itself, and like a wing carries the weight of the plane, the propeller blade carries its fraction of the total thrust of the propeller. The more blades, the lower the fraction of each blade. Low disc loadings are associated with two- or three-bladed propellers. Those can be found on GA aircraft and older, slow designs like ...


6

(Source) Whether the FMS is capable or not of calculating the V-speeds, it should be checked and may be overridden. It is because the airplane database wouldn't know if there's a temporary crane that will affect the climb limit weight, or if 400 ft of the runway are unusable due to maintenance, for example. In other words, 10,000' corrected-length runways ...


5

I would think the OAT in the example is what your on-board thermometer is showing, so at 12,500 ft, not at sea level. ISA is +15°C at sea level, but at 12,500 ft it is -9.8°C, so you are just -10 off ISA. Let's see. 4 ⋅ 12.5 ⋅ (−10) = −500, so the formulas match. Note though, that this is still just an approximation. The temperature lapse rate might also ...


5

You do not calculate indicated airspeed: It is an indicated value, you read it from the airspeed indicator. (I suppose you can calculate it if you really want to, but I've got no idea why you would want to do so in the context of flight planning.) You determine what airspeed to use for flight planning purposes using your aircraft's performance data (from ...


5

If you look closely at the example, it's describing a situation where you're cruising at 5500 feet, and landing at an airport with a "pressure altitude" (elevation) of 680 feet. The chart, however, is indexed to zero-altitude. You can't just reduce your cruise altitude by the elevation of the airport, because performance varies with altitude (indicated by ...


5

$V_R$ is: FAR 23 (e.g. multi-engine small planes): $\geq 1.05\;V_{MC}$ (105% of minimum control in flight) $\geq 1.1\;V_{S_1}$ (110% of V-stall for a specific configuration) FAR 25 (e.g. transport jets): $\geq V_1$ $\geq 1.05\;V_{MC}$ Must result in $V_2$ before 35 ft height Must result in $V_{LOF}$ [when the airplane is rotated ...


5

The RTOW (regulatory takeoff weight) charts are runway and configuration specific, so the length and slope (and permanent obstacles) and all taken care of (see red box below). There is no manual formula, either the charts or a performance calculator such as the Airbus FOVE or the company's proprietary software. This is what an RTOW chart looks like: The ...


5

That depends how you define longer in aviation. As you can look at it geographically or on the clock. The hard answer is no, the most fuel efficient route is the one that has the aircraft in the air for the shortest amount of time. If you can take advantage of a big tail wind 20 miles south of the geographically shortest route or at a slightly higher ...


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