Aces High Bulletin Board
General Forums => The O' Club => Topic started by: muckmaw on December 18, 2002, 02:56:04 PM
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Here's the deal. I volunteer at an aviation museum and I'm whats called a Costumed Interpreter...meaning, I wear all the flight gear and walk around talking about the planes, etc.
Now, I was never given any training, so I rely on my own studies to gather info, but there are some things I just cannot find.
Any chance of getting some help on these questions?
1. Are fighter cockpits pressurized? If so, why do pilots wear oxygen masks. If not, why the oxygen mask below 10k?
2. Whats the difference between the Air National Guard, and the Air Force and Air Force Reserve.
3. How many Gs do you pull when you eject?
4. How long does it take to learn to fly for the military?
5. Why does one book say the A-10's rate of fire on the GAU-8a is 4200 RPS, and another says 2000 RPS. Is it adjustable?
Thanks in advance.
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I believe I can help with the first question.
Modern Combat Airplanes do have pressurized cockpits, but just to a certain altitude pressure. You have to understand that the greater the difference between the external and internal pressure, the more the structure has to withstand... if the cockpit pressure was to be set to sea level pressure, the canopy would eventually break due to excessive tension.
So why pressurize it at all? Well, while the pilot cannot breath the lo-press oxygen at 33.000 feet, the body does appreciate the higher pressure.
As for the oxygen masks, pilots must breath oxygen for some 30 to 45 minutes before going to high altitudes in order to break any nitrogen bubbles that we all have, and that would cause severe problems if they were to grow in size due to reduced pressure.
I'm sure eagl will answer this question (and of course the rest) much better than me, but let this serve you as an introduction ;)
Daniel
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Originally posted by CyranoAH
As for the oxygen masks, pilots must breath oxygen for some 30 to 45 minutes before going to high altitudes in order to break any nitrogen bubbles that we all have, and that would cause severe problems if they were to grow in size due to reduced pressure.Daniel
This is interesting...classic "bends" prevention, which makes sense, I guess.
What is considered "high altitudes"?
If this is the case then you couldn't scramble fighters to intercept really high bogies if they are within a calculated distance from the base, right? The pilot would get seriously "bent" if he went up too fast?
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Originally posted by CyranoAH
I believe I can help with the first question.
Modern Combat Airplanes do have pressurized cockpits, but just to a certain altitude pressure. You have to understand that the greater the difference between the external and internal pressure, the more the structure has to withstand... if the cockpit pressure was to be set to sea level pressure, the canopy would eventually break due to excessive tension.
So why pressurize it at all? Well, while the pilot cannot breath the lo-press oxygen at 33.000 feet, the body does appreciate the higher pressure.
As for the oxygen masks, pilots must breath oxygen for some 30 to 45 minutes before going to high altitudes in order to break any nitrogen bubbles that we all have, and that would cause severe problems if they were to grow in size due to reduced pressure.
I'm sure eagl will answer this question (and of course the rest) much better than me, but let this serve you as an introduction ;)
Daniel
Well you learn something new everyday. I'd always thought the O2 mask was for helping combat G forces etc. or something along those lines.
Tronsky
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Originally posted by muckmaw
5. Why does one book say the A-10's rate of fire on the GAU-8a is 4200 RPS, and another says 2000 RPS. Is it adjustable?
switch
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Curval, the space shuttle goes from 0ft sea level to outer space in like 10 minutes.. I'd guess it wouldn't be much dif than a jet scrambling against intruders.
(dunno, just offering an observation)
-SW
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Originally posted by AKS\/\/ulfe
Curval, the space shuttle goes from 0ft sea level to outer space in like 10 minutes.. I'd guess it wouldn't be much dif than a jet scrambling against intruders.
(dunno, just offering an observation)
-SW
But surely the space shuttle is pressurized "at sea level"?
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Hell if I know.
-SW
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Well...thing is when you see those astronauts on tv doing their fancy floating around astronaut stuff, they never wear oxygen masks...hence my theory that the cabin is pressurised @ sea level.
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Prolly right, I didn't really think that far ahead. On launch they are typically fully suited (helmet 'n all).
-SW
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Most cockpits are pressurized to somewhere between 0.6 and 0.8 atmospheres. I guess military generally go lower than this.
Depends on the type of pressurization. You need to ensure an adequate supply of oxygen to the pilot, easiest way of doing this is to give it to him directly through a mask. Oxy systems into the cabin require more (heavy) eqiptment.
How may G's you pull on eject varies. Depend on the seat but can be anything from 20-30g ish over a small space of time. Generally the newer seats pull higher G but the way they are built means the pilot stands a much better chance of coming out of it with no injuries.
I'll have a look at my background docs from the RAF, I'll post on the 'how long does it take to qualify' thing tomorow if no one else does.
Gatso
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I guess astronauts are suited up on take-off in the case something goes wrong which could lead to immediate depressurization - what is all but healthy...
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Kirin's got it....There is not much volume inside a pressurized cockpit of a fighter. Loss of pressurization at high altitude would render the pilot breathless(Payne Stewart Airplane). The Military knows they aren't there for a picnic, so they are combat ready when the wheels leave the ground.
Thorns
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Originally posted by muckmaw
1. Are fighter cockpits pressurized? If so, why do pilots wear oxygen masks. If not, why the oxygen mask below 10k?
They're pressurized starting at 8k MSL to maintain a cabin pressure of 10k up to a certain altitude (about 25k I think, then it increases at a slower rate to avoid bursting the cockpit as mentioned earlier). The regs say O2 isn't required below 18K, and I drop my mask as often as I can. We refer to it as "the squid" cause it feels like one's stuck to your face ("It's sucking my will to live!"). A lot of guys will drop their masks below 18-10k, running the risks of facial injuries in an ejection, but after a couple of hours of smelling the chilli dog you had for lunch and having the skin rubbed off the bridge of your nose, it's nice to take a break.
In the event of a rapid decompression due to malfunction/battle damage a person's TUC or time of useful consciousness without an oxygen supply at high altitudes is reduced to seconds. Basically you black out before you even know what happened due to the oxygen level of your blood dropping below the necessary level to stay awake. It's been theorized that the crew of Payne Stewart's plane experienced a rapid decompression and couldn't get their emergency O2 masks on in time and passed out at high altitude. The plane's windows were fogged up from the inside as reported by the F-15's scrambled to intercept it, a common feature of rapid d. If the plane was on autopilot, it would take quite awhile for it to descend to thicker air, by which time unconsciousness would have led to death at the oxygen-scarce higher altitudes. Tragic.
Additionally, in cases of high altitude ejection, the seat (I'm talking ACESII) will stay with you until lower altitudes allow a safer chute opening. So while you're falling with your seat from 50K to around 20k your O2 mask alows you to breathe using the seat's emergency O2 bottle, without which you'd be unconscious from a lack of oxygen by the time your chute opened.
2. Whats the difference between the Air National Guard, and the Air Force and Air Force Reserve.
Insert punchline here.
3. How many Gs do you pull when you eject?
I think it's around 23 G's for an ACES II seat.
4. How long does it take to learn to fly for the military?
Typical fighter track:
Joe College gets 30-40 hours in light aircraft from the USAF, basically a free private pilot's license before going to UPT or undergraduate pilot training, which in the USAF takes 12 months. He's then sent to IFF or introduction to fighter fundamentals where he begins his tactical training in AT-38's (T-38's with gunsights and bomb racks). This is a 2 month course after which he's sent to an FTU or formal training unit which is teaches him to fly his particular fighter aircraft. Some courses last 6 months (F-16) to nine months (F-15E). By the time he gets to his fighter unit he's got about two years invested.
5. Why does one book say the A-10's rate of fire on the GAU-8a is 4200 RPS, and another says 2000 RPS. Is it adjustable?
Our gun has a high and low rate of fire (F-15E) which we can select in the cockpit. We've been running in it in low rate to prevent jams. Can't speak to the Hog's cannon. Some guys at work came from the A-10 though, I could ask them.
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Thanks ZAP!
Thats some great info I can pass on to the tourists.
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1 has been answered, I can help with the A10. The exact number on the cannon's rate of fire is classified so books are estimates. That's the reason for the disparity from text to text on most modern weapons.
I am not 100%, but it takes approximately 2 years from the Academy for most students to enter duty as a pilot.
The Differance between the Air Guard, and the Reserves are simple. The Air Guard are state forces, and the reserves are fedral. It takes the president to activate local Guard forces, for other then state emergencies. There are acceptions and but that is the general rule.
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Muck.
I saw an A10 close up at an aircraft museum at Pima,AZ. I was told by one of the staff that the A10 cannon has two rates of fire - fast, and faster! The fast rate is 70 rounds per second, and the even faster rate was given as 150 rounds per second.
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Here's another one, showing the whole plane. They had about four of these up doing training when I was there. Note how the nosewheel has to be offset to accommodate the gun...
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Originally posted by beet1e
Muck.
I saw an A10 close up at an aircraft museum at Pima,AZ. I was told by one of the staff that the A10 cannon has two rates of fire - fast, and faster! The fast rate is 70 rounds per second, and the even faster rate was given as 150 rounds per second.
I wonder if I still have my tech manuals on the Gau-8. There are two rate of fire settings for the gun (switchable in the cockpit), but 9000 rounds per minute seems high if memory serves correctly.
AKDejaVu
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Just did some checking at the http://www.af.mil web site on the A-10 (http://www.af.mil/news/factsheets/A_10_OA_10_Thunderbolt_II.html). 3900 rounds per minute seems to be the only setting available now. Several other web sites mentioned a lesser speed option that was done away with in the 80's with a particular modification. My manuals would not have shown this.
So... it does not seem to be a switchable thing anymore. They'll just have to settle on 3900 rounds per minute of 30mm depleted uranium tipped bullets.
AKDejaVu
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BTW, Muckmaw...
The difference between the Guard and the Reserve is that the Guard is basically a state entity while the reserve is federal. Both are very similar in their "reserve" mode, but the Guard can be activated by the state governer. Also, full time Guard members are not paid in the same manner as full time Active Duty or Reserve members. They're paid more along the lines of state employees for regular work... though they switch to federal pay if actually deployed.
There's actually much more to it than that... but the Guard is basically each state's militia with the Governer of the state acting as the commander in chief... though they still fall under federal control when all is said and done.
AKDejaVu
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Hummmm ... A10:D
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Ask eagl about modern fighters, the USAF occasionally lets him fly an F15. That is, when he isn't lounging in bed. :)
dago
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Curval: The pilot would get seriously "bent" if he went up too fast?
As seriously as ascending from a dive to 33 feet.
miko