# Tag Info

74

The engine in a typical light airplane (say a Cessna 172 or a Piper Cherokee) has a lot in common with the engine in a classic 1960s VW Beetle (Type 1): Both engines are horizontally opposed four-stroke four-cylinder spark ignition gasoline engines. Their parts even have similar metallurgy, and broadly similar failure rates. In fact if you remove the gearbox ...

52

Surface air temperatures aren't really going to be relevant for an airliner. The temperature of the troposphere doesn't vary that much. In fact, the troposphere is warmer at the poles (from Wikipedia Troposphere): At middle latitudes, tropospheric temperatures decrease from an average of 15 °C at sea level to about −55 °C at the tropopause. At the poles, ...

33

They could, if only they were allowed to. From § 121.161 Airplane limitations: Type of route. (a) Except as provided in paragraph (e) of this section, unless approved by the Administrator in accordance with Appendix P of this part and authorized in the certificate holder's operations specifications, no certificate holder may operate a ...

31

Much like water, exposing fuel to below freezing temperatures does not instantly make it freeze. It takes some amount of time, and as long as the fuel is not exposed to below freezing temperatures long enough to make it freeze, it won't be a problem. How much time? That depends on a number of factors like: Type of fuel Jet A (common in the US) has a ...

31

There are two primary factors that affect the skin temperature of an aircraft in flight: the air temperature, and the speed of the aircraft. The air temperature where airliners cruise is relatively cold, around -54 °C at 35,000 feet. As a body like an aircraft moves through air, it compresses the air, which causes the air temperature to rise. The maximum ...

29

To avoid overheating, the usual trick is to select the right material: The Concorde used a special aluminium alloy, called Hiduminium, which had higher strength at elevated temperatures and allowed the Concorde to cruise at Mach 2.02. Aluminium melts at 660°C. The MiG-25 used stainless steel instead of aluminium to make its top speed of Mach 3.1 possible (...

29

From the A320 Flight Crew Operating Manual (FCOM): And the image to text: On ground, hot weather conditions may cause overheating to be detected around the bleed ducts in the wings, resulting in “AIR L (R) WING LEAK” warnings. Such warnings may be avoided during transit by keeping the slats in Configuration 1 when the OAT is above 30 °C. (Emphasis mine) ...

28

Norwegian’s heat issues stem from an unusually high passenger capacity aboard the Boeing 787-8 jetliners that the carrier uses on its Las Vegas routes. Most airlines operate the plane with an average of 200 seats, but Norwegian puts 291 seats for sale on the 787-8 aircraft to keep costs down as part of its low-cost model. Given the weight of those ...

24

This depends entirely on how you depressurized it. Depressurizing the aircraft by fully opening the outflow valve will lower the temperature somewhat, but will not bring it to that outside. The expansion process will be closest to free (Joule) expansion, which causes only small decrease in temperature, not an adiabatic one that corresponds to the ...

22

Apart from the paragraph you quoted, here are a few more reasons. Dry nitrogen is specified for aircraft use. I believe the rules say that any gas used cannot exceed 5% oxygen content. Because its dry it reduces corrosion. Nitrogen moleculeas are slightly larger than oxygen and takes longer to escape.. hence tyres stay inflated longer. But more importantly, ...

21

Short Answer Very high temperatures limit how much payload and/or fuel you can load on a plane. Engines To help you visualize it, in hot air the air molecules are more energetic, which means the engine will have hard time compressing hot air vs. cool air. Losing thrust. Wings Hot air—with the molecules spaced farther apart—has less density, which ...

20

As you measure temperature moving at high velocities, your outside thermometer will measure a higher temp than what is actually outside (what a non-moving thermometer would get). That's because as the air rams into your thermometer it gets a little bit compressed, and that makes it heat up a little bit. Amazingly, some smart people have even calculated how ...

19

1. The combustion chamber Temperature here is usually controlled via design of the chamber shape, in particular of the location where combustion occurs vs the airflow. Image source In the image above you can see that the fuel line (2) terminates in a nozzle. The nozzle will turn the fuel into tiny droplets to increase the surface area and hasten the ...

19

To add some more aspects to voretaq7's answer: Airplane engines have a very different operating point than car engines. This makes it impossible to simply plug a car engine into an aircraft. Aircraft piston engines have a max. RPM of 2700. Since they are normally directly coupled to the propeller, a higher engine speed would reduce propeller efficiency. ...

15

Aircraft performance is a many-faceted topic. Insofar as it being so hot that operation is prohibited, a couple of things come to mind. Aircraft performance figures are supplied by the aircraft manufacturer, typically as tables, up to a certain temperature. Since operators are required to use those tables for determining the aircraft's ability to safely ...

14

As DeltaLima said, the change in brightness is probably due to the difference in lighting. The first picture is above the clouds, so the air is clear and the light is primarily from the sun. The second picture is in the clouds, so the air is moist and the light is much more diffuse, coming from all directions. This diffuse lighting and the moisture on the ...

11

The atmosphere approximates an ideal gas, and as such you can relate pressure and density through the ideal gas equation. The form we use in meteorology uses mass density and is given by: $$p={\rho}RT$$ where $P$ is pressure in units of Pa, $\rho$ is density in units of kg m-3, $R$ is the gas constant for dry air (287 J kg-1 K-1) and $T$ is temperature in ...

11

Many things including bottles containing liquids break when the temperature drops below zero, so the cargo hold is always maintained above freezing; 7°C is typical (source). This applies to both pure cargo aircraft and mixed passenger/cargo airplanes. That said, it's harder to control for (say) cargo sitting around on tarmac while waiting to be loaded ...

11

Both images you posted are of Pratt&Whitney J58 afterburning turbojet that was used on the Lockheed A-12 and Lockheed SR-71 aircraft. That engine ran particularly hot. The engine was designed for operation at Mach 3.2. The efficiency of turbojet increases with speed, but only to a certain point and somewhere above Mach 2 it starts to decline. However ...

11

There is some truth in the claim about inerting. Mostly, blowouts are as a result of high temperatures weakening the rim and tyre and increasing gas pressure within it, rather than being the result of chemical explosions. However, overheated tyres can decompose to produce gaseous products that can explode in air at high pressure and temperature and there ...

11

In addition to what the current answers mention, it should be noted that the danger is not merely theoretical, though blowouts on touchdown aren't necessarily the primary concern. Mexicana flight 940 was the deadliest 727 accident as well as the deadliest accident on Mexican soil with 167 deaths. Accident investigators found that a tire had been serviced ...

10

Cold weather definitely affects the performance of helicopters (as it does all aircraft), because it affects the density of the air they move through. I will ignore icing so let's assume dry air. The lift equation is: $$L = \frac{1}{2} \rho V^2 S C_L$$ $L$ = Lift $\rho$ = density of the air. $V$ = velocity of the aerofoil (rotor) $S$ = the wing area ...

9

The reported altimeter setting, QNH, is 'somewhat' corrected for temperature, in that it corrects for temperature error at the aerodrome elevation. This is the main difference between the more-meteorologicaly-inclined QFF which does not contain this temperature correction. You will still get altimeter errors because of the high/low temperature while being ...

9

Quick answer: At the design point considered, which is assumed to be takeoff conditions, a CFM56-5C combustor raises gas temperature to 1360°C (the share of the compressor in this raise is about 600 °C). This is a common value found in modern turbine engines, a balance between fuel consumption reduction and turbine material capabilities (nickel super-alloy, ...

8

I'd like to answer with a focus on the SR-71, since I happen to have a book that gives details on its design. Ben Rich was the lead of the propulsion and thermodynamics group for the SR-71, and Kelly Johnson's successor as head of the Skunkworks for later programs. In the "Faster Than a Speeding Bullet" chapter of his memoir Skunkworks (pg 203 in the first ...

8

One point that seems to be missing from excellent answers provided so far is carb heat. Carburetor icing is a concern for most if not all carbureted aircraft. The small planes I've flown (Cessna 152/162/172) all have a manual carb heat knob. When you engage it, the engine's air intake is switched over to air that has been warmed by the exhaust. This is ...

8

The fresh air vents near your head at each seat can not be adjusted for temperature individually. Cabin temperature is controlled. Just ask a Flight Attendant to warm it up as they have a control panel to adjust cabin temperature by zone. Most modern airliners use bleed air from the engines to power two Air Conditioning Packs which circulate cooled or ...

8

The temperature of the environment doesn't have a significant impact on the performance of a rocket engine. Air breathing engines have better performance in cold air because the mass density is higher at a given pressure, which allows them to ingest more air, and because the thermodynamic efficiency of a heat engine increases when the temperature of the cold ...

8

In the troposphere, air at altitude is colder than air at ground level. But surprisingly, air at altitude at the poles can be warmer than air at altitude at the equator. From the wiki article on troposphere (I added the bullet points): The troposphere is heated from below by latent heat, longwave radiation, and sensible heat. Surplus heating and vertical ...

7

Most Jet engine fuel systems have means to heat the fuel to prevent it from freezing. Typical heat exchange methods followed are by employing hot air or hot oil taken from the engine. Reference: FAA Aviation Maintenance Technician Handbook, Chapter 14: Aircraft Fuel System

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