You say that as if outrunning a storm in an airplane would be difficult. Really, though, it’d be difficult to not outrun it. The storm has no engines, so it must be at rest relative to the ambient airspeed, while the plane is moving relative to the air.
Any fighter plane has to be extremely strong by definition. The airframe has to be able to withstand a high g-load and the severe punishment of a dog-fight. They are largely built out of non-corrosive airframe components as well. That is the difference between, say, cars and airplanes. A car from the 1950’s is considered to be an antique and a museum piece. Airplanes from that era not to mention ones as far back as the 1930’s (like the DC-3) are still used as working machines. Airframes have an indefinite life-span as long as they are maintained (not necessarily replaced peicemeal either).
Anyway, it isn’t like the average owner of a P-51 Mustang is going to fly it enough to worry about metal fatigue. Metal fatigue may be a problem in airplanes that have been flown 10’s of thousands of hours. Even 10,000 hours represents it being flown for an hour a day for 27 years and that just doesn’t happen with an old warbird bought for fun and show.
The problem isn’t usually what speed the wheels can handle, but the finite length of the runway, and possibly obstructions beyond that which must be cleared (usually at least a barbed wire fence, sometimes power lines within a 1/2 mile, trees, etc) There is also normally a wind gradient, so you lose a few knots airspeed as you are climbing (trying to climb!) the first 10-30’ or so.
Landing a hang-glider with a tailwind REALLY sucks!
And to answer the obvious question: (why would ya?) On fairly calm days, convection can cause a pretty stiff breeze to pop up with no warning, thus you can start a take-off into the wind, and have it turn into a tailwind just as you start to roll.
i would need to see a cite on this because I don’t believe it.
In the first place, building a plane just strong enough to withstand the aerodynamic forces for some definite period of time would be diffcult, if not impossible. You don’t know what those forces are without an extensive testing program and even that would be only statistical information.
In the second place, throw-away airplanes would creat a big logistical problem because of the continuous supply of planes that would have to be shipped overseas.
Let me rephrase that. Instead of :
He could either take off into a T-storm and try and outrun it, or he could sit at the end of the runway and ride it out. He chose the latter.
It should be:
He could either try to take off into a T-storm and outrun it, or he could sit at the end of the runway and ride it out. He chose the latter.
The thunderstorm was already on top of him before he took off.
As far as the durabiltiy of a WWII fighter plane, my cite is my dad’s friend who owned a Mustang. He said that it costs him about $800/hr to fly that plane. That is not the price of gas, it is the price to keep the thing flying.
If I take a step back, it doesn’t make sense that it would be the airframe that would wear out that quickly.
What would make sense is that they would use a high horsepower engine that would eat itself up pretty quickly. An overhaul on a 12 cylinder engine can’t be cheap. I don’t if that is what he meant or not.
Right. They say if you want to know what hobby aircraft ownership is like, build a big fire in your backyard, throw all your money into it, and if you have fun, owning a hobby plane is for you. $800 an hour doesn’t seem unreasonable at all. The problem isn’t the airframe. The engine has a TBO (Time between Overhaul) of about 600 hours with a mini-TBO at 300 hours. That is bad by today’s standards and would cost tens of thousands of dollars each time. However, that isn’t to say that you have to hand over $800 each time you fly it for one our. That is an average over time.
A P-51 is a fairly simple machine designed with a strong airframe and easy to maintain controls and control surfaces. Any maintenance is very expensive but that doesn’t mean that they are replacing parts left and right or that the aircraft is largely unoriginal.
That sounds a lot better. Yes, the engines on all warplanes in WWII, not just fighters, got the max power out of the min weight so they were stressed right to the max. Engine rebuilding and switching was an ongoing operation.
As a side light. At the beginning of the war the army decided that they were going to make sure that planes had top-notch, reliable engines. So they replaced engines with a rebuilt after a certain number of hours. To their chagrin reliability went down. The old “infant mortality” gottem.
In any manufacturing, assembly process there will be a certain number of defective parts, mistakes in assembly, or even inadvertent damage in assembly. So when an engine is rebuilt, some of them will fail quickly. The army changed to the method of running the rebuilts in on a stand (which they should have done in the first place) and leaving them in until it showed the early signs of wearout, such as excessive oil consumption, failure to maintaim rpm on the runup magneto test, etc.
And as to costing $800/hr. I don’t think that’s out of line. Every plane we had was tended to by a whole crew of specialists. There was a crew chief, and someone for engines, airframe, controls, hydraulic, electrical, communications and maybe the fuel system.
Every morning the crew gave all systems a thorough checkout to make sure it was as ready to fly as could be.
I get a whole slew of aviation magazines and I still find myself gasping sometimes when I look at maintenance and ownership figures. The $800 an hour figure isn’t because a P-51 is an antique or especially troublesome because of age. I would expect something similar for a modern plane of roughly the same design. The P-51 consumes about 60 gallons per hour of fuel at cruise. Avgas costs about $5 a gallon right now so there is $300 an hour right there. However, people don’t buy P-51’s just to putt around in them. Fuel consumption goes way up as they show off and have fun. Nope, $800 doesn’t sound out of line at all especially once you think in terms of aviation economics. I have to pay $100 per hour to fly around rather slowly in an entry-level two-seater.
Sure, at the expense of altitude (or potential altitude if you happen to be in some lift at the time.) If you’re allowed to descend in the turn then you don’t need to increase the load factor either. The only reason the load factor increases is because it needs to to maintain level flight. When you turn you must give something up. It can be either speed, altitude, or fuel.
When talking about the speed of sound, the indicated air speed alone is no longer a factor. An aircraft (that goes fast enough) has a Mach meter which uses indicated air speed and local air pressure to compute the aircraft’s speed as a fraction of the local speed of sound. This is quite accurate and so the indicated speed of sound is essentially the same as the actual speed of sound.
What I was saying is that shockwaves develop well before the aircraft reaches the speed of sound. This is because the wing works by accelerating air over the upper surface. This means that there are local sections of airflow that are travelling a lot faster relative to the aircraft than the aircraft is through the whole air mass.
The air travelling over the upper surface of the wing will reach the speed of sound at somewhere between Mach 0.7 and Mach 0.8 (or 70% to 80% of the speed of sound.) This speed is when shockwaves start to form and is the start of the speed range known as “transonic.”
A certain amount of aircraft design involves delaying or minimising the formation of these shockwaves. A swept wing is one design feature that achieves this. A swept wing doesn’t accelerate air as much as a straight wing. Other methods include flattening the top of the wing which also reduces the acceleration of air.
Well, I’d imagine for a beginner, or someone who’s never really thought about it…
- Taking off is hard
- A tail wind ‘helps’ you fly.
- Thus, I want to take off with a tail wind.
Quoth Scalar Weapon:
No, a wing works by deflecting air downwards. Many wing designs do incidentally also accelerate air over the upper surface, but this is not inherent to the way the wing actually works. I would have thought that a seasoned SDMB veteran like yourself would have seen one of the previous threads on this question.
I’m familiar with discussions on the topic. I’m pretty sure that regardless of what is responsible for the lift, all wings do accelerate air over the top surface, even if it is a flat plate inclined at an angle. Otherwise they’d be able to design wings that didn’t develop shockwaves until Mach 1.
Since both an aircraft in level flight and one descending at a constant rate must develop lift equal to their weight, you can limit the increased load factor in a turn only by accelerating downward (possible, but rarely practical).
True, the increased load factor is required to maintain equilibrium, not necessarily level flight.
Too tight a turn to final has killed many an airplane.
In light aircraft, an extremely tight turn can be made if you are able to give up altitude. By maintaining an above average speed to use after leveling out to stop the rate of decent without stalling enables one to make some really quick and useful approaches. **::Do NOT try this without knowing your aircraft really, really well and doing a lot of practice at altitude.:: **
*:: Our insurance required 3000 hours not just in type but in that particular aircraft. Got a heck of a deal since we both qualified for that. (Owner and myself) Took it to 5000 hours after he quit flying and I had the time. (He would do anything to save a buck.)::: *
The heavier the aircraft, the more attention must be paid to sink rates. Ask the big Iron guys, they can tell you all about momentum and resistance to changing directions.
It may push it up from the ground more, but it doesn’t change the mass. I think you’re kind of confusing “weight” with “mass”.
Doesn’t do either. As noted above, once off the ground, a steady headwind or tailwind has no effect on a plane’s flying qualities.
Correct. Once again, this is like the theory of relativity where reference points can change depending on what is referencing it. In a plane’s case, the reference point is primarily the air and not the ground. Sustained air movement in any direction doesn’t affect the plane’s flying abilities at all. The plane is immersed in the air and that is all it knows. That is why planes can fly in hurricanes rather safely. The plane doesn’t know it is in a hurricane. A sustained 150 mph wind is the same as no wind because the wind is measured in relation to the ground and the plane always sees it as 0 mph. Only the airspeed in relation to that counts.