Let’s say, entirely hypothetically, you’re out for a gentle cruise over the South China Sea in your four-engine propeller-driven patrol plane. It’s a beautiful day and you’re on autopilot at 20,000 feet going about 180 knots.
While you’re tooling around taking in the sights and sounds (and whatever stray electronic emissions may come your way), a pair of jet fighters from a nearby communist country come up and start hot-dogging around you. One of them decides to play chicken, and see how close he can come to your left wing.
As he is approaching you, his horizontal stabilizer hits you outboard left propeller. Propeller fragments strike your nose cone, which flies off and impacts your inboard right engine. Shrapnel pierces your pressure bulkhead.
The plane rolls around 130 degrees (about 3/4 of the way to fully upside down) and takes a severely nose down attitude. You look straight up, and see the surface of the sea, along with the flaming remains of the jet fighter plummetting into the ocean with the pilot bailing out.
OK, now that you’re in this hypothetical situation, what do you do? How difficult an evolution is it to gain control of the aircraft? Is this the sort of thing that is covered in training or flight simulation? How incredible a feat of airmanship is it to keep the aircraft together and land it at a nearby airfield?
Thank St. Amelia I’ve never been in that situation!
Recovery from “unusual attitudes” is taught as part of the flight training curriculum. As I was taught, the procedure would be to reduce power on the engine(s) and roll the wings level; then pull out of the dive.
When you roll the wings level, you will pitch down. That’s why you reduce the power on the engine(s): so you don’t over-stress the airframe when you pull out. Aircraft have what’s known as V[sub]ne[/sub] which is the “never exceed” speed. There is a safety margin built in, but that can be easily exceeded in an emergency situation. There is also V[sub]va[/sub] (maneuvering speed), which is the speed below which abrupt and extreme control movements are possible (though not advised) without exceeding the airframe’s limiting load factors.
That’s the way I was taught emergency night landings if you have an engine failure - set up a best rate glide, and as you near the ground turn on your landing light. If you like what you see, go ahead and land. If you don’t, turn off your landing light.
As for the OP, Johnny’s got it right. Power to idle to prevent overstressing the airframe, roll the aircraft rightside up, and pull out of the ensuing dive.
If you’re aerobatically trained, and the aircraft is going really fast, you might start by pushing forward on the column to arrest the dive while inverted, then rolling it upright. But this requires special training, because putting force on the control column while rolling the aircraft is a good way to wind up in a spiral dive or a snap-roll, either of which will ruin your day in an airplane like the P-3.
But complicating all this is the fact that, with the nose gone, you’re going to have a bunch of turbulent air causing havoc with your flight controls and lifting surfaces. So you don’t know what your stall angle might be, and the controls are probably getting banged around in your hands. I heard that the pilot said it took all the strength he had to keep the airplane flying.
Also, he probably lost the pitot tube, which means his flight data instruments are going to be completely out of whack. He’d have to fly by groundspeed using GPS rather than airspeed, which would be tricky. I’ll bet the needles of all his pitot-static instruments were bouncing all over the place. Depending on where the avionics are stored in the aircraft, he may have also lost GPS, Radar, etc.
All in all, it sounds like he did a great job getting that plane on the ground in one piece.
Speaking of unusual attitudes, they are the direct cause of many crashes. One of the more common scenarios is like the crash of JFK. Jr. A pilot loses visual references and succumbs to vertigo. (I’ve had vertigo while in IMC – dad was a CFII and I was technically “in training” – and it is very uncomfortable to “know” you’re in a bank but trust your instruments that you are not.) He thinks he’s in a bank so he “corrects” and really does enter a bank. His senses then tell him he’s in a bank again, so he “corrects” more, tightening the turn. This is called the “graveyard spiral”. A couple of things might happen if the pilot does not recover. One is that the spiral continues until the aircraft hits the ground. Another possibility is that the spiral tightens to the point that the aircraft is basically headed straight down and succumbs to aerodynamic stresses. A third possibility is that the pilot sees the ground coming up quickly and attempts to pull sharply out of the dive. Such abrupt maneuvering may literally rip the wings (or tail surfaces) off of the aircraft.
Oh, I forget to mention in my hypothetical that you’ve lost your pitot tube and radar, though you do have GPS (or some other manner of determining groundspeed).
By the way, what is a pitot tube (and what are pitot-static instruments)?
The vertigo scenario sounds scary, but could you translate your parenthetical for the non-aviators among us?
IMC is “instrument meteorological conditions”. CFII (“CF-double-eye”) means “certified flight instructor - instruments”. In order to fly in IMC (or IFR - “instrument flight rules”) you need to be properly rated. To get the training for your IFR rating, you train with a CFII.
For a taste of vertigo try this: Sit in a swivel chair. Put on a blindfold and raise your feet. Have an assistant twirl you around in one direction or another. Give the “thumbs up” sign with your hands resting on the armrests or your knees. Point with your thumbs in the direction of your turn. Pint your thumbs up when you stop turning. Observers will note that you are signaling a turn well after your motion has stopped. Switch places with your assistant so you can observe it for yourself.
While instruments can and do fail, an IFR-certified aircraft will have backups, and with training you can use your primary flight instruments (that are working) to get to a safe place.
I was flying in IMC for about two hours. My mind was screaming at me that I was in a left bank. Over and over I’ve heard the phrase “trust your instruments”. I did. I watched the artificial horizon, altimeter, airspeed, and directional gyro. It was a difficult thing to “fly the instruments” contrary to what my body was telling me, but I did it. Eventually the cloud tops became ragged and I could catch glimpses of the black and starry sky. Even these glimpses helped my body orient itself. The cloud tops became lower and I flew on over the undercast with no further disorienting effects. (Note: If the cloud tops are uneven – that is, if they have a “slope”, you may try to “level” the aircraft based on what you perceive as “flat ground”. That can be disorienting, but since I’m not IFR rated I haven’t run into it.)
Disorientation can happen even on a bright clear day. A friend of mine was a Blackhawk pilot in the 101st Airborne during the Gulf War. She said that it takes special attention to fly over a featureless desert. I learned to fly in the Mojave Desert and never got disoriented, but that was in an airplane. I flew helicopters over the same desert and learned that I had to pay attention to my altimeter. Five hundred feet seems a lot higher when there are few buildings and lots of sand. Although I noted the perception of altitude and adjusted my perception to account for it, I can see how people could fly a perfectly good aircraft into the ground.
A pitot tube is a probe that sticks out of the airstream of the aircraft. If you go to your local airport you will usually see these under the wing. They are unpainted L-shaped probes about six inches long. Aw, heck. Here’s a definition from http://beadec1.ea.bs.dlr.de/Airfoils/glossary.htm
As stated, there is a “static port” in the airframe. It is a disc with a “pin hole” in it that lets the air collected by the pitot tube out of the system.
The pitot-static system operates such instruments as the airspeed indicator and vertical speed indicator. Here’s a page with a description: http://pws.prserv.net/uncletom/gs/pitot.htm
There are a number of pilots on this board. (There’s a thread in IMHO taking a poll.)
[sinister voice] Join ussssss…! [/sinister voice]
Johnny’s only slightly wrong in his description of the pitot-static system - the static port is not a vent that lets out air from the pitot tube. The ram air from the pitot tube does not vent into the static system at all, or it would screw up all the readings.
The static port is actually a source of external air pressure. The ports are located on the aircraft specifically so they do NOT allow any ram air into them. They are usually flat disks with pinholes in the middle, that are shallow enough to stay inside the boundary layer on the fuselage (the boundary layer is a very thin layer of air that is slowed down by friction. Right at the surface, it is not moving at all).
That, plus the pinhole size of the static port itself, keeps ram air out of the system under normal conditions. But if you sideslip the airplane and present the static port to the relative wind, you will get a slight pressurization. Those of you who are pilots, try it some time. Slip the airplane while watching the VSI. You’ll see it jump.
Some instruments, like the Airspeed Indicator (ASI), are connected to both the pitot system and the static system, because the ASI works by comparing the ram air from the pitot tube to the static pressure of the atmosphere (if you block either the static port or the pitot tube, the ASI will act like a crude altimeter).
One other small niggle – the pilot does not have to pull on the column to overstress the airplane when levelling the wings out of a spiral dive. One of the dangerous things about the spiral is that the trim airspeed of the aircraft is increasing. In other words, the airplane wants to stay in the spiral, even at a very high speed.
As soon as you level the wings, however, the aircraft wants to return to its trimmed wings-level airspeed. This will cause a rapid pitch-up even if the pilot doesn’t pull back on the column at all. So it’s a good idea to push FORWARD on the column when levelling the wings, to prevent the rapid pitchup that might tear the wings off. Then SLOWLY ease out of the dive. But if you’re going fast enough in the spiral, you might not have enough power in your arms to prevent the resulting pitch-up.
Pitot probes are also handy in many kinds of experimental fluid mechanics situtations for measuring wind speeds.
Like Sam Stone said, you really need info from both pitot and static probes to measure airspeed. Many experimental rigs have both on the same piece of equipment, to get (something like) a point measurement of speed.
Say you want to measure the freestream speed of your wind tunnel. A pitot-static probe would be this L-shaped tube thingy that you’d stick into the tunnel, with the tip of the “L” facing upstream. There’s a hole (or several) in the very tip (the pitot part), and some more holes along the sides of the tube, just behind the tip (the static part). These two sets of holes are not connected inside the tube; they are kept separate and there are two holes at the top of the gadget for attaching pressure gages, or tubes leading to pressure gages, or whatever.
The static holes measure only the local ambient pressure; they’re not “in the wind”, so to speak. The pitot holes measure the ambient pressure (can’t escape that) plus the “dynamic pressure” - essentially, the ram pressure of the incoming airstream. With both of these pressure measurements, you can get the airspeed:
The difference between the pitot and static readings is the stagnation pressure: [sup]1[/sup]/[sub]2[/sub]DU[sup]2[/sup]. If you know the density of the air (reasonably constant, and you can get a better estimate if you’ve got a thermometer & barometer in the room), you can get the wind speed from this:
U = (2 * (p[sub]P[/sub]-p[sub]S[/sub]) / D)[sup]1/2[/sup]
Now, these things aren’t perfect. The static pressure readings can be somewhat off, and these things can be sensitive to misalignment if it’s bad enough. There are books out there on just how to correct for stuff like this, if you’re really serious about it (as some are). They also tend to be a little slow to react to changes in speed, and so aren’t the best for rapidly-varying flows.
There are certainly better techniques out there for more precise measurements of flow speeds, but for just getting a nice freestream reading, pitot-statics are great. They’re low-tech, easy to set up, and reliable.
Brad_d posted some wonderfully precise stuff about pitot tubes and static ports, but there’s a gap between the theory and the practice.
The pitot/static set up varies between planes. The Cessna 150’s I fly have an L-shaped pitot tube outboard and underneath on one wing and a static port just in front of the pilot’s side door, a small disk with a pinhole in the middle. The Piper Warriors I fly have a wedge-shaped piece of aluminum outboard and under one wing with a pitot opening on the front and a static pinhole in the rear of it.
The ram-air pitot and static ports are subject to error. This can arise from where they are positioned on the plane, how fast the plane is going, and what you are doing with the airplane. A sideslip can change pressure over a static port (either increasing or decreasing) and pitot tube, meaning your airspeed indicator and altimeter will not give you and exact reading. Unusual attitudes can result in unusual numbers. For instance, with full flaps a C150 stalls somewhere in the high 40s (I can’t for the life of me remember the damn number tonight and don’t have the POH handy). At the point it stalls, however, although the airspeed is definiately up there, the airspeed indicator reads 0 due to where it is on the plane and the way the air currents around the plane change when on the edge of a stall. The manual for a plane usually has a section on when your airspeed instrument will read funny and by how much.
Oh, wait - for those of you who don’t fly, a stall is when you’re flying so slowly the wing no longer generates enough lift to hold you up in the sky. This can range from almost a non-event to something that actually feels like you’re falling out of the sky, depending on circumstances.
Going back the OP sceanario:
The only I can relate this to are the spins I’ve been through. In the Cessna 150 I was in all cases, spin entry results in a nose-down attitude 70 degrees relative to the ground and a rotation around the long axis of the plane of up to 30 rpm. A bunch of other stuff happens, too, but those two are generally the first you notice, unless you’re watching the airspeed register 0 and the altimeter unwinding at high speed as you head earthward. This will really get your attention.
Even if your expecting it, this manuver can be alarming. If you aren’t expecting it, in a case such as a mid-air collision, the pilot may or may not delay in recovery. Once the pilot figures out whats going on and how to fix it (which, depending on training and experience, can be anywhere from “almost instantly” to “never”) recovery from the sort of dive described in the OP is pretty straight forward - level the wings, make sure you have proper airspeed, and gently pull out of the dive. If you’re actually upside-down it’s a matter of having the presence of mind to roll the plane over so it’s upright again.
Keep in mind that there are a lot of pilots who fly upside-down or do spins for the fun of it. What cranks the tension up is the unexpected nature of an accidental unusual attitude.
Another factor is the plane itself. Some airplanes are more suited to flight in usual attitudes than others. An aerobatic or fighter plane is designed to take high g’s and fly in bizarre atitudes. Other planes are not and might break up in some situations, or become uncontrollable. For instance, some airplanes will not recover from spins.
A third thing to consider in this sceanario is damage to the plane itself. If control surfaces are damaged or jammed by a collision it can severely complicate the problem of recovery, or render it impossible. A multi-engine plane with a damaged or unusuable engine will also complicate control problems to at least some degree. Structural damage could also render a plane less resistant to g forces.
So, although recovery from unusual attitudes is something covered to one degree or another in any pilot’s training (and presumably more so in a military pilot), the combination of unexpected collision and damage to the airplane makes the the survival of an airplane in such circumstances a demonstration of great piloting skills.
Just in case a budding pilot is reading this thread …
Actually, a aerodynamic stall occurs whenever the angle of attack (AOA - the angle between the relative airflow and the wing chord) exceeds the critical stall angle which is ~15-20 deg IIRC for most airfoils. This can occur at any airspeed and attitude, not just slow flight. It occurs during slow level flight (stall speed) because the angle of attack must be increased to compensate for the loss of lift at low airspeeds. Once the AOA exceeds the critical value, the air flow breaks up on the top of the wing, lift drops rapidly, and the nose drops. More than one pilot has flown into the ground well above stall speed (accelerated stall). The first time you do an accelerated stall you will be glad it was NOT pulling out of a low dive (c.f. buzzing runway/SO’s house). Make sure you try this at altitude and BELOW Va (and adjust for gross weight)
When I was in training my instructor told me to bring the Cessna 172 into a stall while operating at full power. I slowed the aircraft by retarding the throttle and used my elevator control to maintain the specified altitude. Once I was slowed I advanced the throttle, eventually firewalling it. I continued to slow by raising the nose. I had the yoke all the way back and the aircraft would not stop flying or even lose altitude. When I reached for the trim wheel the instructor said to forget it; I’d done everything I could to stall the aircraft and it wouldn’t do it. I don’t remember if the flaps were deployed.
Don’t get me wrong; Cessna 172s, like any aircraft, can be stalled. Many have with unfortunate results. Performing stalls is part of learning to fly (and, like autorotations in helicopters) they can be a lot of fun. Just make sure you have enough altitide. If you inadvertantly stall an aircraft, make sure you are current in recovery.
There are some stall and spin resistant designs. One of the first (the first?) was the Aeronca Ercoupe. Many don’t even have rudder pedals. Burt Rutan had a lot of success in the 1970s and 1980s with the Vari-Eze/Long-EZ (pronounced “Easy”). These aircraft had canards that would stall before the wing, which would lower the nose and allow the wing to keep flying. On the other hand, IIRC, spins were prohibited in the Grumman Yankee because the fuel would be driven out to the wingtips making it difficult or impossible to recover. (If I got that wrong I’m sure someone will be along presently with a correction.)
“Flying in itself is not inherently dangerous. But to an even greater degree than the sea, it is terribly unforgiving of any carelessness, incapacity, or neglect.” I think the hypothetical fighter pilot proved that in the hypothetical situation. But you could always be run over by a speeding icecream truck while you’re crossing the street.
I owned a Grumman AA1B (Newer version of the Yankee) for 8 years. I loved that plane.
The fuel thing is partly true. In the AA1, the fuel tank is contained within the spar, which is just a hollow tube. So yes, if you get into a spin the fuel can slosh out to the ends of the wing and increase the gyroscopic moment of the airplane. But I did the math one day to figure out how much fuel would have to be in the airplane to get the maximum effect, and it turned out to not have all that much of an effect.
A bigger problem in spin recovery is the short-coupled fuselage (small distance between the wing and tail), and the small rudder. That, coupled with a fairly unforgiving airfoil, caused all the trouble. The fuel sloshing made it worse.
NASA used an AA1 for spin recovery studies. They found that the aircraft could be recovered every time if recovery was started in less than (I believe) a turn and a half. But if you let the spin develop beyond that, it would start to go flat and the rudder wasn’t big enough to stop the rotation. The spins could get so unrecoverable that NASA actually lost an AA1 when the pilot had to bail out because the thing wouldn’t recover from a spin even after the anti-spin drag chute was popped out the back.
I put my AA1 into incipient spins, and lots of stalls. It had reasonably gentle stall characteristics (not as compared to something like a 172, but as compared to other high performance airplanes like Mooneys and Bonanzas).
But the airplane is an absolute joy to fly. Fingertip pressure on the controls, a roll rate better than some aerobatic planes, bubble canopy, and a pretty high cruise speed (135 mph in mine, on 108 hp. A Cessna 152 with the same engine is lucky to break 115). It has a high wing loading, and therefore penetrates turbulence well. It’s also very roomy (the fuselage is 42" wide - 5" wider than a Cessna), and very, very strong. The spar is overbuilt, and the fuselage is made of a honeycomb steel sandwich. It can’t be tapered, so it’s much stronger than it needed to be. I don’t think one has ever broken up in flight. I saw a photo of the aftermath of a windstorm, with a Cessna 177 FOLDED over the top of a Grumman Cheetah (big brother to the AA1, same construction). The Cheetah looked fine, although splayed out on its gear, and the Cessna was demolished.
In 8 years, I never put more than $600 in the airplane in any given year. It simply came through its inspections with no work required, every time. And it had the smoothest 4-cylinder engine I’ve ever flown behind.
But don’t lose the engine. The AA1 has all the glide capability of an aerodynamic brick. I flew out of a military base, and they let us do overhead break approaches. I used to fly over the field at 2500’ AGL, pull the power to idle, and by the time I did a 270 onto final I was almost on the runway.
Still, I’d buy another one in a minute. A lot of them are retrofit with O-360 engines, and those little beasts will go about 160-170 and climb at 1600 fpm. Burning the same amount of gas as a 172. And you can find those for about 20K. And fly with the top down.
Been there, done that, too - yelling “Stall, dammit, stall already!”. Also had a day when I was practicing nice, tame little stalls and accidentally fell into an incipient spin. Cessna are usually well behaved but every now and then they’ll bite you on the butt.
Can’t emphasize enough that stalls are only fun at altitude. Down low, they can really mess up your day.
And yes, Oblio, you are absolutely correct about too much AOA causing stalls and that stalls can occur at any speed or attitude, but I was assuming the non-flyers hadn’t dropped out of discussion and didn’t really want to give anyone an 40 minute lecture on aerodynamics.
Wasn’t aware any of them ever had rudder pedals. The two down at my local field sure don’t.
Now that I read my previous post, I’m not at all sure the Ercoupe was made by Aeronca. Doesn’t sound right. Anyway, I know there are Ercoupes out there with rudder pedals; but I’m not sure how many came that way and how many are retrofits.
Sam Stone: Oh, right! The short-coupled fuselage! I’d totally forgotten about that. I’ve never flown the AA-1, but my first logged hours were in an AA-5. Nice ride.
I will never, ever forget that summer afternoon when I first put a 172 into a full power-on departure stall. The extreme angle of attack and the engine noise were just awesome. I stood that brand new Skyhawk on it’s tail and we floated for what seemed like an eternity in the humid Mississippi sky before she shuddered and departed just a bit, dropping the nose just enough to get a hold in the air again.
Sorry, I broke off on a rant there. Resume normal navigation.
