How to avoid CFIT
https://www.caa.govt.nz/assets/legac...und_Course.ppt
Is this of any interest? There used to be a pdf which I thought more useful but I couldn't find it.
"I've been fortunate to have done most of my flying over a very flat landscape,"
I'd say unfortunate if you're flying for pleasure.
Is this of any interest? There used to be a pdf which I thought more useful but I couldn't find it.
"I've been fortunate to have done most of my flying over a very flat landscape,"
I'd say unfortunate if you're flying for pleasure.
Last edited by Maoraigh1; 17th May 2019 at 21:28. Reason: Add
Discussion here
Max Rate turn vs. Min Radius Turn
Answer explained. Minimum radius is referred to as "corner speed".
http://www.flightlab.net/Flightlab.n...aneuvering.pdf
Max Rate turn vs. Min Radius Turn
Answer explained. Minimum radius is referred to as "corner speed".
http://www.flightlab.net/Flightlab.n...aneuvering.pdf
Moderator
Interesting article Megan. Though I completely accept what it says, it's probably beyond the scope of GA flying in a number of places. Keeping to the "private flying" aspect of things, factors such a G loss of consciousness during maneuvering are unlikely, particularly for the flying pilot. If one were to maneuver a normal category GA airplane to the point of Gloc for the pilot, structural damage and loss of control are certain. It's not a CFIT anymore, it's a loss of control - which can happen, but the factors are different. the article and discussion are very worthwhile, though not really relevant to CFIT prevention.
CFIT is prevented by awareness of proximity to terrain - nothing else.
Collision avoidance, in the most extreme last minute case, might be prevented by abrupt maneuvering. But, honestly, if it's come to that point, you're more likely to lose the control you'd like to maintain, by the abrupt maneuvering. It takes a lot of skill to instantly detect the need for abrupt maneuvering, and execute it without exceedance. It'd be easier to apply a fraction of that skill to not needing to do it in the first place.
In the case of close quarters maneuvering, gentle is better. Only as abrupt as is required. And, presuming you're suddenly trying to avoid an obstacle, you want to be really practiced deliberately flying close to things (a challenging skill). If you've errantly got yourself in that tight, use less abrupt maneuvering to not hit the thing, rather than more abrupt maneuvering to give it a wider clearance. There's no point in maneuvering too abruptly and inducing a stall or loss of control to miss it by a mile, when you could have maintained control well, and missed it by enough.
I trained in a particular mountain area in British Columbia (they know mountains there) flying helicopters. I was mentored into a particularly confined looking dead end canyon. (As I measure it on Google earth, it is a mile deep from entry point to the back canyon wall, and 0.8 miles round, 350 feet below the rim, and 400 feet above the descending floor). For a fixed wing pilot like me, that's really tight - but I was being trained in a helicopter, so flying into places like this was more "normal". I worked in this canyon during several training exercises, and got somewhat used to it. (I really never get used to flying toward something I know that I must turn away from, 'cause I cannot out climb it). Anyway, years later, I was est flying a modified deHavilland Beaver amphibian. The very experienced pilot with whom I was flying entered this same canyon - I was terrified! He was calm as normal. I was still terrified!! He gracefully flew around inside this canyon, and back out the way we flew in ('cause there was no other choice!). Then he flipped the control to my side and said "you do it". My slightly subsided terror returned!!! But I did, The trick was to not get phased by it. I flew the wingtip a hundred feet or so off the trees all the way around, in a very gentle (anything but abrupt) turn, and it was fine. I practiced a few more times, and got more relaxed. When I late expressed my fear of doing that, the mentor pilot validated my sense of self preservation, in not doing that kind of thing unsupervised. Then he went on to tell me that that canyon was where he trained water bomber pilots, in much larger (S2F) twin engined water bombers to enter, and not only turn back out, but water bomb down the middle as they exited. So flying the Beaver a lazy circle around there was easy by comparison. I've flown in that area since, but never flown in that canyon again, though possible, and I have proven it to myself, it is still not worth the risk.
But, that was not a CFIT risk, I was well aware of where the terrain was!
CFIT is prevented by awareness of proximity to terrain - nothing else.
Collision avoidance, in the most extreme last minute case, might be prevented by abrupt maneuvering. But, honestly, if it's come to that point, you're more likely to lose the control you'd like to maintain, by the abrupt maneuvering. It takes a lot of skill to instantly detect the need for abrupt maneuvering, and execute it without exceedance. It'd be easier to apply a fraction of that skill to not needing to do it in the first place.
In the case of close quarters maneuvering, gentle is better. Only as abrupt as is required. And, presuming you're suddenly trying to avoid an obstacle, you want to be really practiced deliberately flying close to things (a challenging skill). If you've errantly got yourself in that tight, use less abrupt maneuvering to not hit the thing, rather than more abrupt maneuvering to give it a wider clearance. There's no point in maneuvering too abruptly and inducing a stall or loss of control to miss it by a mile, when you could have maintained control well, and missed it by enough.
I trained in a particular mountain area in British Columbia (they know mountains there) flying helicopters. I was mentored into a particularly confined looking dead end canyon. (As I measure it on Google earth, it is a mile deep from entry point to the back canyon wall, and 0.8 miles round, 350 feet below the rim, and 400 feet above the descending floor). For a fixed wing pilot like me, that's really tight - but I was being trained in a helicopter, so flying into places like this was more "normal". I worked in this canyon during several training exercises, and got somewhat used to it. (I really never get used to flying toward something I know that I must turn away from, 'cause I cannot out climb it). Anyway, years later, I was est flying a modified deHavilland Beaver amphibian. The very experienced pilot with whom I was flying entered this same canyon - I was terrified! He was calm as normal. I was still terrified!! He gracefully flew around inside this canyon, and back out the way we flew in ('cause there was no other choice!). Then he flipped the control to my side and said "you do it". My slightly subsided terror returned!!! But I did, The trick was to not get phased by it. I flew the wingtip a hundred feet or so off the trees all the way around, in a very gentle (anything but abrupt) turn, and it was fine. I practiced a few more times, and got more relaxed. When I late expressed my fear of doing that, the mentor pilot validated my sense of self preservation, in not doing that kind of thing unsupervised. Then he went on to tell me that that canyon was where he trained water bomber pilots, in much larger (S2F) twin engined water bombers to enter, and not only turn back out, but water bomb down the middle as they exited. So flying the Beaver a lazy circle around there was easy by comparison. I've flown in that area since, but never flown in that canyon again, though possible, and I have proven it to myself, it is still not worth the risk.
But, that was not a CFIT risk, I was well aware of where the terrain was!
If one were to maneuver a normal category GA airplane to the point of Gloc for the pilot
From "Aerodynamics for Naval Aviators"
The aerodynamic limit describes the minimum turn radius available to the airplane when operated at CLmax. When the airplane is at the stall speed in level flight, all the lift is necessary to sustain the aircraft in flight and none is available to produce a steady turn. Hence, the turn radius at the stall speed is infinite. As speed is increased above the stall speed, the airplane at CLmax is able to develop lift greater than weight and produce a finite turn radius. For example, at a speed twice the stall speed,
the airplane at CLmax is able to develop a load factor of four and utilize a bank angle of 75.5° (cos 75.5°=O.25). Continued increase in speed increases the load factor and bank angle which is available aerodynamically but, because of the increase in velocity and the basic effect on turn radius, the turn radius approaches an absolute minimum value. When CLmax is unaffected by velocity, the aerodynamic minimum turn radius approaches this absolute value which is a function of CLmax, W/S, and AoA. Actually, the one common denominator of aerodynamic turning performance is the wing level stall speed.
The aerodynamic limit of turn radius requires that the increased velocity be utilized to produce increasing load factors and greater angles of bank. Obviously, very high speeds will require very high load factors and the absolute aerodynamic minimum turn radius will require an infinite load factor. Increasing speed above the stall speed will eventually produce the limit load factor and continued increase in speed above this point will require that load factor and bank angle be limited to prevent structural damage. When the load factor and bank angle are held constant at the structural limit, the turn radius varies as the square of the velocity and increases rapidly above the aerodynamic limit. The intersection of the aerodynamic limit and structural limit lines is the “maneuver speed." The maneuver speed is the minimum speed necessary to develop aerodynamically the limit load factor and it produces the minimum turn radius within aerodynamic and structural limitations. At speeds less than the maneuver speed, the limit load factor is not available aerodynamically and turning performance is aerodynamically limited. At speeds greater than the maneuver speed, CLmax and maximum aerodynamic load factor are not available and turning performance is structurally limited.
Each of the three limiting factors (aerodynamic, structural, and power) may combine to define the turning performance of an airplane. Generally, aerodynamic and structural limits predominate at low altitude while aerodynamic and power limits predominate at high altitude.
the airplane at CLmax is able to develop a load factor of four and utilize a bank angle of 75.5° (cos 75.5°=O.25). Continued increase in speed increases the load factor and bank angle which is available aerodynamically but, because of the increase in velocity and the basic effect on turn radius, the turn radius approaches an absolute minimum value. When CLmax is unaffected by velocity, the aerodynamic minimum turn radius approaches this absolute value which is a function of CLmax, W/S, and AoA. Actually, the one common denominator of aerodynamic turning performance is the wing level stall speed.
The aerodynamic limit of turn radius requires that the increased velocity be utilized to produce increasing load factors and greater angles of bank. Obviously, very high speeds will require very high load factors and the absolute aerodynamic minimum turn radius will require an infinite load factor. Increasing speed above the stall speed will eventually produce the limit load factor and continued increase in speed above this point will require that load factor and bank angle be limited to prevent structural damage. When the load factor and bank angle are held constant at the structural limit, the turn radius varies as the square of the velocity and increases rapidly above the aerodynamic limit. The intersection of the aerodynamic limit and structural limit lines is the “maneuver speed." The maneuver speed is the minimum speed necessary to develop aerodynamically the limit load factor and it produces the minimum turn radius within aerodynamic and structural limitations. At speeds less than the maneuver speed, the limit load factor is not available aerodynamically and turning performance is aerodynamically limited. At speeds greater than the maneuver speed, CLmax and maximum aerodynamic load factor are not available and turning performance is structurally limited.
Each of the three limiting factors (aerodynamic, structural, and power) may combine to define the turning performance of an airplane. Generally, aerodynamic and structural limits predominate at low altitude while aerodynamic and power limits predominate at high altitude.
CFIT is prevented by awareness of proximity to terrain - nothing else
https://dms.ntsb.gov/pubdms/search/h...D940D0EBE66555
Take note of page 16 at https://dms.ntsb.gov/public/60000-60...163/606411.pdf
Not a laughing matter
https://app.ntsb.gov/pdfgenerator/Re...=HTML&IType=FA
The reported last message from this fatal instruction flight, with a student pilot, appears relevant to this thread. April 2019 accident.
The reported last message from this fatal instruction flight, with a student pilot, appears relevant to this thread. April 2019 accident.
Moderator
flying at Va and turning/banking to point of stall burble would give you 3.8 "g" (normal category limit) and the minimum radius turn, and no ability to overstress the aircraft. No one is going to get G-loc there. It gives you the minimum radius turn,
Va is a wise and safe reference speed for maneuvering - at altitude. If you're in a situation where maneuvering abruptly at Va is your means to best assure a safe exit from the situation, you're way past safe anyway. If the notion is to fly around at Va, so at any moment, you could apply full control input to maneuver around a sudden surprise, well, that's technically correct, but way beyond good airmanship!
This is why this topic is worrisome for an online discussion, it presupposes a lot of cautions which should be a part of a bigger discussion.
If you're in a situation where maneuvering abruptly at Va is your means to best assure a safe exit from the situation, you're way past safe anyway. If the notion is to fly around at Va, so at any moment, you could apply full control input to maneuver around a sudden surprise, well, that's technically correct, but way beyond good airmanship!
https://www.atsb.gov.au/media/577600...-103_final.pdf
Risks abound whatever you do.
The video posted by Megan is a demonstration of gob smacking idiocy. For GA most CFIT accidents seem to start with a progression of VMC into marginal VMC into IMC. I teach my students that before you fly in poor weather you have to set hard limits. I recommend starting with 3 nm in flight visibility and 1000 ft AGL. Determining actual flight visibility is pretty easy with modern GPS moving map displays, if you can't see that geographic feature 3 miles in front of the little airplane on the moving map turn around. The same with altitude, if you can't maintain good VMC at your 1000 ft AGL minimum altitude then turn around.
I also tried to get all my students some exposure to actual marginal VFR conditions. There is a small airfield 11 miles from my home base. to get to it you have to pass over an inlet and up a bay. On several occasions I have had students get spatially disoriented in this short flight. Every student has remarked how difficult 700 and 2 actually was compared to how they thought it was going to be.
I also tried to get all my students some exposure to actual marginal VFR conditions. There is a small airfield 11 miles from my home base. to get to it you have to pass over an inlet and up a bay. On several occasions I have had students get spatially disoriented in this short flight. Every student has remarked how difficult 700 and 2 actually was compared to how they thought it was going to be.
