# Questions tagged [aircraft-performance]

Aircraft performance covers areas such as the amount of runway required to takeoff or land and how fast an airplane can climb or descend.

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### Rate of climb equations for jet + propeller aircraft [duplicate]

For an aircraft with both jet and propeller, how do we calculate the maximum rate of climb? I know the equation of maximum rate of climb, velocity, and angle for propeller and jet, respectively. But I ...
185 views

### Relation between altimeter setting (QNH) formula and the barometric formula

I'm searching for a reliable source for a formulization of the QNH adjustment to the barometric altitude. I found this document from weather.gov that gives a formula for the Altimeter Setting, which ...
161 views

### Is “excess thrust” possible in a steady state vector diagram?

Being recently very much sold on the lift-weight-thrust closed triangle (with weight forming the hypotenuse) model for climbing flight, I proceeded to put the logic through its paces (validation) and ...
116 views

### What does “pitch plus power equals performance” really mean?

It is often said in aviation circles that "pitch plus power equals performance". A. What is it supposed to mean? B. Is it always true? C. If it isn't always true, why is it a useful concept ...
231 views

### Altimeter setting and pressure altitude

Student pilot here. I thought I was smarter than this, I’m struggling with this concept. I got the ASA test prep book and there’s a question asking what happens to the indicated altitude when the ...
69 views

### Is it possible for a higher aspect ratio wing to have increased drag compared to a lower aspect ratio wing of the same area?

Since increasing aspect ratio while maintaining wing area decreases chord, one can expect Reynolds number to decrease. Are there cases in which the resulting increased coefficient of friction would ...
172 views

### How can I find the maximum climb angle of a propeller driven aircraft from a graph of vertical velocity against airspeed?

I've been asked to find the maximum climb angle of a propeller driven aircraft from the graph of vertical velocity against airspeed: How can I do that?
134 views

### Could drag in a turn be twice the drag in straight and level flight?

Just wanted to see if my understanding of drag is correct as I am unsure. I understand that during straight and level flight, the drag can be calculated as: With the first term being the parasitic ...
73 views

### Determining the total drag of a propeller driven aircraft while turning with a load factor of n = 2?

I understand that the total drag includes the parasitic and induced component, with the parasitic component being the same as with straight and level flight. How do I calculate the induced component? ...
218 views

### How does downwash affect angle of attack?

Many aerodynamics textbooks, as well as many answers on here and similar websites claim that the downwash downstream of a wing induces a net angle of attack that is lower than just looking at flow ...
164 views

### Barrel Roll Airliner Landing [duplicate]

Can this barrel roll in an airliner be ferformed by a skilled pilot? Is this real?
432 views

### How do power and thrust curves compare?

I would like to really understand why when talking about jets we care about thrust but when talking about propeller aircraft we care about power. (THRUST)="Just a force" (POWER)= work/time = ...
107 views

### Why is one exhaust directed upwards? [duplicate]

This is the first Cessna Skycourier during certification. Why are the two exhausts oriented upwards?
227 views

### Roller Coaster Airline

Could an airliner legally (using a common regional jets or less likely airliners) and safely perform acrobatic maneuvers that would otherwise not be permitted for commercial passenger flights. Why? ...
324 views

### Can Airbus A400M take-off from the beach fully loaded?

I've recently saw this footage. Airbus A400M tactical capabilities on natural surfaces by performing take-off, landing and taxiing manoeuvres. I wonder if she could take-off fully loaded from that ...
67 views

### What is the difference between Line-Replaceable Unit (LRU) and Line Replaceable Modules (LRM)? [duplicate]

i am studying Line-Replaceable Unit (LRU) and Line Replaceable Modules (LRM) but do not know the difference.
103 views

### Are there any characteristics of a hypoxic flight? [closed]

Any patterns that investigators look for? For example, what happens when the engine flames out? is it guaranteed to enter a high speed dive? And would this affect certain parts of the aircraft, ...
446 views

### How can L/D Max be both Best Glide speed and Max Range speed?

According to the book "Aerodynamics for Naval Aviators", best glide speed AND max range speed for propeller aircraft both occur at L/D max. This is a little confusing because in an A36 ...
55 views

### In symmetrical airfoils is the stall angle the same for negative AOAs as for positive ones? [duplicate]

In symmetrical airfoils is the stall angle the same for negative Gs as for positive ones? Let say the stall angle is 17 degrees AOA. Is it the same if you push the nose down?
100 views

### Landing at 30,000 ft [duplicate]

Excluding how a runway would exist at 30,000 ft, could landing a plane at that altitude be done? What would it take to do so? Very Basic Wind rose for Mount Everest Weather Phenomena That Could ...
138 views

### How does altitude affect the TAS and thrust of an electric fan powered aircraft?

I'm confused about the relation between IAS, TAS, thrust, and shaft power, for an electric application. Yes, higher air is thinner, and thrust goes down due to higher airspeed. What I've researched ...
79 views

### Can I use Stihl fs250 engine for ultralight aircraft? [duplicate]

RPM 9000 Hp 2.2 Engine weight 6kg Plane weight 40kg Body weight. 70 Propellers(2blades) length 30 inches Wings length 120 inches
262 views

### What is the minimum speed at which the Antonov An-2 can maintain level flight?

The An-2 famously has "no stall speed", as control can be maintained in descent at arbitrarily low airspeed. As wikipedia says: The An-2 has no stall speed, a fact which is quoted in the ...
200 views

### Does Green Dot Speed Calculation include banking Angle?

I'm wondering, whether the Green Dot- speed calculation in the Airbus PFD does account for the actual bank angle of the aircraft. ...
159 views

### What happen if the glide slope beacon removed for maintenance? [closed]

it about aircraft navigation system (ILS), when the aircraft about to landing but unfortunately the glideslope beacon being removed.
201 views

### Why are the best glide and best range airspeeds different for a C172?

According to Cessna 172 POH the speed for max range with power off, or glide speed, is 65, and achieved at the best L/D ratio. However with power on the speed for max range will be around 75. Why is ...
92 views

### How does altitude affect drag? [duplicate]

Consider two aircraft. Aircraft A flying at sea level with weight (W) and Angle of attack (α). Aircraft B flying at altitude h in level flight at the same weight (W) and same angle of attack (α) (same ...
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### What is the engine shell temperature?

What are the highest temperature locations in the outer shell on an aircraft engine? Particularly, modern turbofans like the Trent 900 for example. I'm interested in the temperature constraints of ...
48 views

### Why max thrust without afterburner is called military power? [duplicate]

The jets before the merge starts with military power, which means max thrust before ab.Why named that way?
92 views

### Does thrust output in jet airplane remains constant when altitude increases?

I’m a noob so sorry for my ignorance. The question is: do we need (in jet airplane) to increase the throttle to maintain constant thrust output if we want to fly higher (not considering climb phase), ...
154 views

### Why can airliners not fly as fast as fighter jets? [duplicate]

Why do passenger aircraft not fly at the speed of fighter jets? What factors stop them from achieving such speed?
624 views

### Is “takeoff distance” measured over the ground, or to a point in the air?

I read that takeoff distance was the distance for which the airplane is on the runway, as well as the distance for which it ascends to 15 meters off of the ground. Does it get measured as the ...
49 views

### If the VVI, FPM, airspeed indicator somehow failed you can use fuel flow to help you with your attitude (climbing or descending)?

If the VVI/attitude indicators , FPM, airspeed indicator somehow failed same time and now you could not get cross control check, can use fuel flow counter(because of the decrease consumption rate) to ...
213 views

### Will it be more efficient if airplanes flap like birds? [duplicate]

Many airplanes have parts that are designed to mimic some features of animals. I have also read that birds are incredibly more efficient than most of the airplanes we see today. I wonder, will the ...
134 views

### What is the mathematical relationship between Specific Excess Power and an aircraft's acceleration at a given point on an E-M diagram?

If an aircraft is on the x-axis of an E-M diagram plot (zero turn rate) where the Specific Excess Energy (Ps) = 800, we understand this to mean that the aircraft has the potential to either ...
120 views

### Can briefly explain the principle behind the inversion on this power required curve?

I’ve noticed on several graphs in the “Advanced Pilot’s Flight Manual”, that power available is lower for any given speed at 10,000 feet as compared to sea level flight. The power required curves ...
93 views

### Which among the two contributes most of the lift, the upper or lower surface of the airfoil? [duplicate]

I see some explanations that lift is due to the suction of low pressure on the top surface of the wing and deflecting down of airflow on the bottom which results to upward force lift. I wonder, which ...
174 views

### Why does drag coefficient decrease with Mach number in the supersonic regime?

I'm trying to understand why the drag coefficient decreases in the supersonic regime with Mach number. While it is easy show this using supersonic, potential flow theory, I'm looking for a more ...
3k views

### Why can we not use full throttle in a C172 when cruising at lower altitudes?

My flight training manual (FTM) says that at low altitudes we throttle back our trainers in order to not exceed recommended power settings. But why is that? Is the air close to sea level just too ...
139 views

### On an energy-maneuverability (E-M) diagram how does the shape of a specific excess power (Ps) curve change as thrust is increased or decreased?

Most E-M diagrams for high-performance aircraft show a "dog house" plot with turn rate on the Y axis and velocity on the x axis. They may also have additional lines for constant turn radius ...
536 views

### What type of airfoil do low-supersonic aircraft use?

I understand that supersonic airfoils have better performance supersonically, but it seems at if they are not always used for any aircraft that goes supersonic and that supercritical airfoils are ...
256 views

### Why are true and indicated airspeed different?

So, I understand that True air speed is the motion of aircraft relative to air around it. And, indicated airspeed is speed arising due to dynamic pressure. Considering a true airspeed of 100 knots, ...
204 views

### Can an aircraft climb with the thrust line below the line of flight? [closed]

"Downthrust" is a common engine mount feature of propeller driven aircraft, models and full scale alike. From model building experience and flight, downthrust, angling the (tractor) engine ...
1k views

### Flex temperature isn't actually “fooling” the FADEC, right?

I'll be using Airbus terminology here because that's what I know, but I guess the concepts are universally applicable. The way I understand flex temperature is: It's a user interface for pilots to ...
302 views

### Is it possible for Mig 21 at corner speed to extend the flaps to minimize the turn radius? Or this is not an option?

The corner speed is around 330knots if you want to turn better than the enemy is possible to lower the flaps?
120 views

### Did the Mig 21 have differential stabilators to help the ailerons?

The MiG 21 had all-moving tailplanes or stabilators. When rolling, did one stabilator pitch up and the other down to act as secondary ailerons and help the main ones on the wing?
2k views

### What is the difference between nautical air miles and nautical ground miles?

What is a simple way to understand the difference between the nautical air mile (NAM) and the nautical ground mile (NGM)? How does the wind affect the net displacement of the aircraft as that is the ...
88 views

### Why are the wingtips of the Fairchild-Republic A-10 bent downward? [duplicate]

Why are the wingtips of the Fairchild-Republic A-10 bent downwards?It is subsonic aircraft .