5 ms·

Also on aircrafts: https://en.wikipedia.org/wiki/War_emergency_power https://en.wikipedia.org/wiki/War_emergency_power

by captn3m0 6y ago

irontinkerer 6y ago
“ the P-51H Mustang was rated at 1,380 hp, but WEP would deliver up to 2,218 hp” Wow!
- linsomniac 6y ago
  Indeed. I forget where I read it, but it provides that power increase for (IIRC) some small double digits number of seconds before you need to throttle back, or the engine eats itself. If you are able to make it back to base, and that WEP wire is broken, the engine needs a rebuild before it flies again. Definitely an impressive power boost though.
  - tomatotomato37 6y ago
    The MiG-25 also have something similar where the engine redline is marked around Mach 2.8, but there's no system stopping the pilot from keeping it maxed to somewhere above Mach 3 but damaging the engine in the process. Funnily enough I believe the SR-71 has the opposite problem, where the engines would merrily go above Mach 3.5 with no issue but the airframe and everything attached to it would get torn apart by the intense heat if the pilot tried to go any faster
    - chipsa 6y ago
      No, SR-71s are still limited by engine temperature. They measure the Compressor Inlet Temperature, but I suspect that actual limitation is the turbine inlet temp. That said, it'll merrily try to go above that without issue if you don't throttle back. Additionally, there's the Mach Cone. The shock wave off the nose forms a cone shape, with the angle determined by the speed of the aircraft. From the nose to the wingtip forms an angle of about 17.5 degrees, which corresponds well with the max speed from the CIT of Mach 3.3. That both methods of determining max speed agree shouldn't be surprising. Skunk Works was filled with good engineers.
    - p_l 6y ago
      MiG-31 has limiter on engine controls connected to airspeed and mach number indicators, because the engine will happily run above Ma 3, with no issues. The airframe, however, will get bent from temperature and you better hope the missile cooling loops don't fail. The power isn't dialed down at lower speeds in order to provide thrust for maneuvering and climb.
Unklejoe 6y ago
We use something similar on turbocharged drag (grudge) racing cars. The boost controller has a "scramble" button which overrides the preset boost targets and allows you to run a higher (and unsafe) boost level as long as the button is pressed. This is useful when you're in the middle of a $10,000 race and you're losing by a few feet.
- segfaultbuserr 6y ago
  What, this is real?! I already thought it was a Hollywood movie plot.
  - Unklejoe 6y ago
    Yes, definitely real! Although what you're probably thinking of is nitrous oxide injection. One popular manufacturer of nitrous oxide systems is "NOS", which was featured heavily on the Fast & Furious movies. The "scramble" button I'm talking about is for "boost", which is the amount of positive air pressure inside the intake manifold. Both "boost" and nitrous can dramatically increase power by essentially getting more oxygen into the combustion chamber, but nitrous is a much more dramatic effect.
  - bluGill 6y ago
    All motorcycle mechanics have a sign "speed costs money, how fast do you want to go". It isn't a joke, most of them can get as much power out of a 500cc motor as industrial engines get out of 19 liters. The catch is that you have to rebuild the engine every 10 hours of operation, while the industrial engine will run non-stop for many years.
    - blaser-waffle 6y ago
      Those industrial engines also don't turn you into a meat crayon if you make a minor screw-up.
      - bluGill 6y ago
        Sure they do, run away engines are a real problem. They will sometimes start using their own oil as fuel, and at that point you better run. (modern engines have safety air shutdowns)
kitteh 6y ago
A320 and B737 had special thrust bump modes for short fields like KSNA. Going back many years to the P&W JT8D you could operate in the red provided you did it for only a certain amount of seconds and logged it down.
- repiret 6y ago
  In general aviation aircraft it’s quite common for there to be time limits on the highest power setting.
  - p_l 6y ago
    There's a maximum power mode selectable on the FADEC interface, which gives you at least 30 minutes of engine life - any use means the engine needs total overhaul. This mode is pretty much reserved for go around or post V1 takeoff when one engine on twin engined airliner had failed.

Also on aircrafts: https://en.wikipedia.org/wiki/War_emergency_power https://en.wikipedia.org/wiki/War_emergency_power

irontinkerer 6y ago

“ the P-51H Mustang was rated at 1,380 hp, but WEP would deliver up to 2,218 hp” Wow!

linsomniac 6y ago
Indeed. I forget where I read it, but it provides that power increase for (IIRC) some small double digits number of seconds before you need to throttle back, or the engine eats itself. If you are able to make it back to base, and that WEP wire is broken, the engine needs a rebuild before it flies again. Definitely an impressive power boost though.
- tomatotomato37 6y ago
  The MiG-25 also have something similar where the engine redline is marked around Mach 2.8, but there's no system stopping the pilot from keeping it maxed to somewhere above Mach 3 but damaging the engine in the process. Funnily enough I believe the SR-71 has the opposite problem, where the engines would merrily go above Mach 3.5 with no issue but the airframe and everything attached to it would get torn apart by the intense heat if the pilot tried to go any faster
  - chipsa 6y ago
    No, SR-71s are still limited by engine temperature. They measure the Compressor Inlet Temperature, but I suspect that actual limitation is the turbine inlet temp. That said, it'll merrily try to go above that without issue if you don't throttle back. Additionally, there's the Mach Cone. The shock wave off the nose forms a cone shape, with the angle determined by the speed of the aircraft. From the nose to the wingtip forms an angle of about 17.5 degrees, which corresponds well with the max speed from the CIT of Mach 3.3. That both methods of determining max speed agree shouldn't be surprising. Skunk Works was filled with good engineers.
  - p_l 6y ago
    MiG-31 has limiter on engine controls connected to airspeed and mach number indicators, because the engine will happily run above Ma 3, with no issues. The airframe, however, will get bent from temperature and you better hope the missile cooling loops don't fail. The power isn't dialed down at lower speeds in order to provide thrust for maneuvering and climb.

Unklejoe 6y ago

We use something similar on turbocharged drag (grudge) racing cars. The boost controller has a "scramble" button which overrides the preset boost targets and allows you to run a higher (and unsafe) boost level as long as the button is pressed. This is useful when you're in the middle of a $10,000 race and you're losing by a few feet.

segfaultbuserr 6y ago
What, this is real?! I already thought it was a Hollywood movie plot.
- Unklejoe 6y ago
  Yes, definitely real! Although what you're probably thinking of is nitrous oxide injection. One popular manufacturer of nitrous oxide systems is "NOS", which was featured heavily on the Fast & Furious movies. The "scramble" button I'm talking about is for "boost", which is the amount of positive air pressure inside the intake manifold. Both "boost" and nitrous can dramatically increase power by essentially getting more oxygen into the combustion chamber, but nitrous is a much more dramatic effect.
- bluGill 6y ago
  All motorcycle mechanics have a sign "speed costs money, how fast do you want to go". It isn't a joke, most of them can get as much power out of a 500cc motor as industrial engines get out of 19 liters. The catch is that you have to rebuild the engine every 10 hours of operation, while the industrial engine will run non-stop for many years.
  - blaser-waffle 6y ago
    Those industrial engines also don't turn you into a meat crayon if you make a minor screw-up.
    - bluGill 6y ago
      Sure they do, run away engines are a real problem. They will sometimes start using their own oil as fuel, and at that point you better run. (modern engines have safety air shutdowns)

kitteh 6y ago

A320 and B737 had special thrust bump modes for short fields like KSNA. Going back many years to the P&W JT8D you could operate in the red provided you did it for only a certain amount of seconds and logged it down.

repiret 6y ago
In general aviation aircraft it’s quite common for there to be time limits on the highest power setting.
- p_l 6y ago
  There's a maximum power mode selectable on the FADEC interface, which gives you at least 30 minutes of engine life - any use means the engine needs total overhaul. This mode is pretty much reserved for go around or post V1 takeoff when one engine on twin engined airliner had failed.