Cessna 150 crash at Vereeniging
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Cessna 150 crash at Vereeniging
I attended the FAVV airshow held on the weekend. Having a discussion about how underpowered a Cessna 150 is, we saw a Red & White Cessna 150 Take-off on runway 03. It then got airborne after using just over half of the runway - which is kind of normal for a C-150.
Several seconds later there was a dust cloud about 4 miles after the runway - we then realised the Cessna had crashed. Not sure whether it was due to engine failure, or just that they couldn't get airborne.
The Bell Jetranger was warming up to do a display, so it could immediately be dispatched along with paramedics. Fortunately nobody was injured (there were 2 people onboard).
Earlier that day we saw a C-210 almost hitting the ground on take-off as it battled to get airborne, and at an altitude of no more than 50' the pilot elected to turn to the right, which happened to be downwind. It's extremely important to keep the gear out for as long as there's runway to land, and to gain sufficient altitude before executing a turn downwind, especially is the aircraft is near gross weight.
Several seconds later there was a dust cloud about 4 miles after the runway - we then realised the Cessna had crashed. Not sure whether it was due to engine failure, or just that they couldn't get airborne.
The Bell Jetranger was warming up to do a display, so it could immediately be dispatched along with paramedics. Fortunately nobody was injured (there were 2 people onboard).
Earlier that day we saw a C-210 almost hitting the ground on take-off as it battled to get airborne, and at an altitude of no more than 50' the pilot elected to turn to the right, which happened to be downwind. It's extremely important to keep the gear out for as long as there's runway to land, and to gain sufficient altitude before executing a turn downwind, especially is the aircraft is near gross weight.
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Phew sounds like an interesting day! Thankfully nobody hurt!
The 210 incident was even scarrier in that the turn downwind at very close to stall speed is not clever. Furthermore if you look at the 210 retraction system, you will see that the wheel rotates during the cycle and at a stage the form drag will increase significantly due to the fact that the wheel is almost sideways as it enters the well. The older 210's were even worse in that they had doors that opened cusing a large increase in drag. If you are flying close to the stall it can be enough to bring you into a very uncomfortable situation, close to the ground....
The 210 incident was even scarrier in that the turn downwind at very close to stall speed is not clever. Furthermore if you look at the 210 retraction system, you will see that the wheel rotates during the cycle and at a stage the form drag will increase significantly due to the fact that the wheel is almost sideways as it enters the well. The older 210's were even worse in that they had doors that opened cusing a large increase in drag. If you are flying close to the stall it can be enough to bring you into a very uncomfortable situation, close to the ground....
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Solid Rust Twotter
I know a lot of people have some very unscientific ideas about downwind turns, to say the least. However, Sir C is correct that a downwind turn shortly after TO near the ground is not a clever idea. Remember that close to the ground in a CLIMBING downwind turn the aircraft will be turning into an INCREASING tailwind component due to wind gradient effect. Thus there will be a bleed off of airspeed while the aircrafts accelerates - the greater the windspeed and the steeper the climb out the more pronounced the effect. Pulling up the gear in a 210 at the same time is definitely not a particularly clever thing to do - plenty of 210 s have had propstrikes due to pilots pulling up the gear just after rotation.
I know a lot of people have some very unscientific ideas about downwind turns, to say the least. However, Sir C is correct that a downwind turn shortly after TO near the ground is not a clever idea. Remember that close to the ground in a CLIMBING downwind turn the aircraft will be turning into an INCREASING tailwind component due to wind gradient effect. Thus there will be a bleed off of airspeed while the aircrafts accelerates - the greater the windspeed and the steeper the climb out the more pronounced the effect. Pulling up the gear in a 210 at the same time is definitely not a particularly clever thing to do - plenty of 210 s have had propstrikes due to pilots pulling up the gear just after rotation.
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wheelie
Once you've rotated and have achieved flight you are operating in a moving mass of air that has the same characteristics regardless of whether you're at 2000' AGL or 20' AGL. The only difference would be some rotor activity from upwind obstacles at low level. Turning at low level will have the same effect just above the stall as will turning at altitide, ie none whatsoever.
Once you've rotated and have achieved flight you are operating in a moving mass of air that has the same characteristics regardless of whether you're at 2000' AGL or 20' AGL. The only difference would be some rotor activity from upwind obstacles at low level. Turning at low level will have the same effect just above the stall as will turning at altitide, ie none whatsoever.
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One thing I don't think I made very clear in my initial post was that the C210 almost hit the ground. Whatver the theory around the subject - the fact of the matter is, that if the Cessna 210 maintained runway heading to 200', then turned out, I don't see the same scenario.
Two years back there was a Cessna 177 crash at FAWB, killing all 3 people onboard. The guys were just under gross, and started a downwind turn just as they got airborne, and slammed into the ground.
As to the Cessna 150 Reg. - I'm not sure, it's red & white, and I think it's a ZU reg.
Two years back there was a Cessna 177 crash at FAWB, killing all 3 people onboard. The guys were just under gross, and started a downwind turn just as they got airborne, and slammed into the ground.
As to the Cessna 150 Reg. - I'm not sure, it's red & white, and I think it's a ZU reg.
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Downwind Turns
My 2 cents:
The fact that a aircraft loses speed in a downwind turn is true, simply because the momentum of the aircraft is relative to the earth and not the air mass. This is more pronounced the bigger the aircraft.
Cheers
MB
The fact that a aircraft loses speed in a downwind turn is true, simply because the momentum of the aircraft is relative to the earth and not the air mass. This is more pronounced the bigger the aircraft.
Cheers
MB
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Solid Rust Twotter wrote:
"Once you've rotated and have achieved flight you are operating in a moving mass of air that has the same characteristics regardless of whether you're at 2000' AGL or 20' AGL. The only difference would be some rotor activity from upwind obstacles at low level. Turning at low level will have the same effect just above the stall as will turning at altitide, ie none whatsoever."
I take it that you have never experienced the wind gradient effect? Surely you have. This is most noticeable on a steep approach to land in a strong wind. You will find that you either need to add power or continually check the control collumn forward to maintain airspeed. This is due to the fact that surface friction slows the motion of air near the ground - there is a definite difference in the air mass at 20 ft AGL and 2000 ft AGL!
Ever noticed that windspeeds increase as you climb? Winds backing as you climb? All due to surface friction and the gradients are steepest near the ground. If you really want to prove this to yourself, go and fly a steep approach in a glider with the airbrakes full out in a strong wind and watch your airspeed bleed off if you hold a constant nose attitude.
In a low, climbing downwind turn near the ground you will be climbing through a positive wind gradient. ie an increasing tailwind component; you are effectively flying in an accelerating airmass. Since an aircraft has the property of inertia it takes time for the aircraft to accelerate to compensate for the changing speed of the airmass, and until this happens the airspeed will decrease. This is indirectly related to the fact that you are turning downwind.
In a level turn in a uniform airmass at altitude turning downwind will have no effect on airspeed, apart from the loss of airspeed due to the increased drag in banked flight. This is due to the fact that the airmass is in a steady state ie. not accelerating.
Of course low level turbulence and the increased stall speed in a bank don't really help.
Beckers - there is no rule to say that momentum must be measured relative to earth - (the catholic church will probably have me burned at the stake for saying that, Copernicus style!) You can chose any reference frame you want. What matters in a turn is CHANGES in momentum. Momentum, being a vector quantity has properties of both magnitude and direction.
Consider an aircraft with an airspeed of 80 knots flying west into an 80 knot westerly headwind. The groundspeed will be 0kts. If it turns onto a heading of East the groundspeed will now be 160 kts. Change in momentum = Mass of aircraft (M) * (Change in Velocity) = M*(0-(-160)) = 160M
Consider same aircraft turning from West to East with no wind: Change in momentum = M*(80-(-80)) = 160M
Notice that the change in momentum is exactly the same in both cases! The change in momentum in both cases is brought about by the acceleration forces in a turn ie. the centripetal force is accelerating the aircraft (remember by changing direction you are acclerating) Force = Rate of change of momentum. The quicker the rate of turn the more the sunglashes in your back pocket are going to be squashed, regardless of the wind.
Man, I have WAY to much time on my hands. Got to fly more, got to fly more....
Actually on second thoughts, stuff that. Bring on more women and beer...
"Once you've rotated and have achieved flight you are operating in a moving mass of air that has the same characteristics regardless of whether you're at 2000' AGL or 20' AGL. The only difference would be some rotor activity from upwind obstacles at low level. Turning at low level will have the same effect just above the stall as will turning at altitide, ie none whatsoever."
I take it that you have never experienced the wind gradient effect? Surely you have. This is most noticeable on a steep approach to land in a strong wind. You will find that you either need to add power or continually check the control collumn forward to maintain airspeed. This is due to the fact that surface friction slows the motion of air near the ground - there is a definite difference in the air mass at 20 ft AGL and 2000 ft AGL!
Ever noticed that windspeeds increase as you climb? Winds backing as you climb? All due to surface friction and the gradients are steepest near the ground. If you really want to prove this to yourself, go and fly a steep approach in a glider with the airbrakes full out in a strong wind and watch your airspeed bleed off if you hold a constant nose attitude.
In a low, climbing downwind turn near the ground you will be climbing through a positive wind gradient. ie an increasing tailwind component; you are effectively flying in an accelerating airmass. Since an aircraft has the property of inertia it takes time for the aircraft to accelerate to compensate for the changing speed of the airmass, and until this happens the airspeed will decrease. This is indirectly related to the fact that you are turning downwind.
In a level turn in a uniform airmass at altitude turning downwind will have no effect on airspeed, apart from the loss of airspeed due to the increased drag in banked flight. This is due to the fact that the airmass is in a steady state ie. not accelerating.
Of course low level turbulence and the increased stall speed in a bank don't really help.
Beckers - there is no rule to say that momentum must be measured relative to earth - (the catholic church will probably have me burned at the stake for saying that, Copernicus style!) You can chose any reference frame you want. What matters in a turn is CHANGES in momentum. Momentum, being a vector quantity has properties of both magnitude and direction.
Consider an aircraft with an airspeed of 80 knots flying west into an 80 knot westerly headwind. The groundspeed will be 0kts. If it turns onto a heading of East the groundspeed will now be 160 kts. Change in momentum = Mass of aircraft (M) * (Change in Velocity) = M*(0-(-160)) = 160M
Consider same aircraft turning from West to East with no wind: Change in momentum = M*(80-(-80)) = 160M
Notice that the change in momentum is exactly the same in both cases! The change in momentum in both cases is brought about by the acceleration forces in a turn ie. the centripetal force is accelerating the aircraft (remember by changing direction you are acclerating) Force = Rate of change of momentum. The quicker the rate of turn the more the sunglashes in your back pocket are going to be squashed, regardless of the wind.
Man, I have WAY to much time on my hands. Got to fly more, got to fly more....
Actually on second thoughts, stuff that. Bring on more women and beer...
Last edited by wheels up; 14th Sep 2004 at 18:08.
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wheelie
The approach you describe is that of an aircraft in a moving mass of air aiming for a fixed point on the ground. Of course things will go pear shaped. Ignore the existence of the ground and the aircraft's speed through the air will be what counts.
The approach you describe is that of an aircraft in a moving mass of air aiming for a fixed point on the ground. Of course things will go pear shaped. Ignore the existence of the ground and the aircraft's speed through the air will be what counts.
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Wheelie
Old topic but you have me convinced. One question though - what you are saying is that it is better in the southern hemisphere when getting airborne into an airmass that it is better to be making a climbing left turn rather than a right hand turn - good point. (only a bit of tongue in cheeck)
I agree lets stick to chix + dop
Old topic but you have me convinced. One question though - what you are saying is that it is better in the southern hemisphere when getting airborne into an airmass that it is better to be making a climbing left turn rather than a right hand turn - good point. (only a bit of tongue in cheeck)
I agree lets stick to chix + dop
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Gofor: check out which way the water swirls in your bath when you pull the plug and draw your own conclusions. Just don't blame me if you hurt yourself.
SRT: Forget the @#$& turn since this seems to be confusing the real issue, which is climbing downwind at low airspeed and low level through a wind gradient. The effect of the turn is to increase the drag (further decaying airspeed), increase the stall speed and increase the likelihood of a spin when the aircraft stalls.
From the net - The effects described are the same as those observed climbing downwind through a wind gradient:
One of my favorite instructor tips is to remind students to expect an unusually big drop in airspeed during a steep approach on a windy day. Expecting the old reliable FAA Flight Training Handbook AC 61-21 to back me up, I was disappointed. The internet, however, came through. What I had to search under was "wind gradient". Briefly put, wind gradient is the characteristic of the atmosphere to behave as a "sticky fluid". When air moves over a surface the friction of the surface slows the flow rate. Sometimes described as the boundary layer, this region of affected air can be as little as 500 feet over smooth water to as much as 1500 feet over tall buildings. (We'll leave mountains out of this discussion!) University of California Davis has 3 wind tunnels, even one devoted to model turbulent characteristics of the boundary of our atmosphere near the ground. (http://mae.engr.ucdavis.edu/~wind/) See the attached cartoon showing the hapless glider pilot discovering the phenomena of wind gradient. In a glider, closing wing spoilers is the equivalent of adding power.
Obviously on a calm day there is no gradient but on a windy day the difference between the surface wind and the wind at 200 feet can be 10 knots or more! That is to say the speed of the wind near the ground can be considerably less than at 200 feet AGL, for example. Rapidly dropping down into this region before the airplane can re-establish its normal airspeed causes not an apparent drop in airspeed but a real drop with the accompanied drop in lift. Compensating with rapid up elevator causes more drag and lowers the airspeed further!
Wind shear is a term that gets a lot of press these days and airline accidents and GA accidents have numerous references to pilot's or airplane's inability to cope with rapidly changing wind speeds when flying near the ground. Wind shear and wind gradient are kissin cousins. Wind shear is often associated with strong convective activity (thunderstorms) whereas wind gradient is present any time the wind blows. The internet gave numerous sites that discussed the importance of coping with wind gradient but interestingly most of the sites were connected with gliders, ultralights, or powered parachutes. Get the connection here: all fly at relatively low speed. To pilots of these machines an unexpected 10 knot drop in airspeed could spell disaster.
Here is a short scenario that gives flight instructors night terrors. The student, unaware of wind gradient effect, attempts a short field approach (steep and slow) or simply lets a normal approach get on the extreme side. Students and experienced pilots alike tend to begin ignoring the airspeed indicator as the ground nears, sound familiar? Here's where the trouble begins! Old habits jump in the picture and a quick glance at the airspeed triggers a knee jerk reaction: lower the nose! Whoa! The ground is coming up fast: raise the nose! By now the sink rate is high and the airspeed is even lower! Can the landing be saved by elevator alone? Unlikely! Mother nature and panic yankin and crankin have robbed the airplane of the necessary kinetic energy needed for a controlled flare! The only trick left in the bag is POWER! Immediate and significant power, not just an extra hundred RPM. By now the CFI's pulse rate has doubled and his/her hand has already beat the student to the draw.
Realistically, Lear Jet drivers seldom have to think about wind gradient. But to those of us driving around in 100 mph bug smashers wind gradient, or more properly, ignorance of wind gradient could ruin a good day of flying. What's the lesson here? When making slow steep approaches such as for a short field landing be alert for a sudden drop in airspeed just as you get down to the flare zone and take one hand off the yoke an put it on the throttle. In addition, trees and buildings near the runway can cause a "wind shadow" effect. More than once I have noticed this effect when landing on runway 31 at West Bend during winds from the southwest. Short grass strips are sometimes carved out of the woods and are especially prone to this nasty surprise on windy days! So maybe that platitude about carrying and extra 5 to 10 knots isn't so silly after all!
SRT: Forget the @#$& turn since this seems to be confusing the real issue, which is climbing downwind at low airspeed and low level through a wind gradient. The effect of the turn is to increase the drag (further decaying airspeed), increase the stall speed and increase the likelihood of a spin when the aircraft stalls.
From the net - The effects described are the same as those observed climbing downwind through a wind gradient:
One of my favorite instructor tips is to remind students to expect an unusually big drop in airspeed during a steep approach on a windy day. Expecting the old reliable FAA Flight Training Handbook AC 61-21 to back me up, I was disappointed. The internet, however, came through. What I had to search under was "wind gradient". Briefly put, wind gradient is the characteristic of the atmosphere to behave as a "sticky fluid". When air moves over a surface the friction of the surface slows the flow rate. Sometimes described as the boundary layer, this region of affected air can be as little as 500 feet over smooth water to as much as 1500 feet over tall buildings. (We'll leave mountains out of this discussion!) University of California Davis has 3 wind tunnels, even one devoted to model turbulent characteristics of the boundary of our atmosphere near the ground. (http://mae.engr.ucdavis.edu/~wind/) See the attached cartoon showing the hapless glider pilot discovering the phenomena of wind gradient. In a glider, closing wing spoilers is the equivalent of adding power.
Obviously on a calm day there is no gradient but on a windy day the difference between the surface wind and the wind at 200 feet can be 10 knots or more! That is to say the speed of the wind near the ground can be considerably less than at 200 feet AGL, for example. Rapidly dropping down into this region before the airplane can re-establish its normal airspeed causes not an apparent drop in airspeed but a real drop with the accompanied drop in lift. Compensating with rapid up elevator causes more drag and lowers the airspeed further!
Wind shear is a term that gets a lot of press these days and airline accidents and GA accidents have numerous references to pilot's or airplane's inability to cope with rapidly changing wind speeds when flying near the ground. Wind shear and wind gradient are kissin cousins. Wind shear is often associated with strong convective activity (thunderstorms) whereas wind gradient is present any time the wind blows. The internet gave numerous sites that discussed the importance of coping with wind gradient but interestingly most of the sites were connected with gliders, ultralights, or powered parachutes. Get the connection here: all fly at relatively low speed. To pilots of these machines an unexpected 10 knot drop in airspeed could spell disaster.
Here is a short scenario that gives flight instructors night terrors. The student, unaware of wind gradient effect, attempts a short field approach (steep and slow) or simply lets a normal approach get on the extreme side. Students and experienced pilots alike tend to begin ignoring the airspeed indicator as the ground nears, sound familiar? Here's where the trouble begins! Old habits jump in the picture and a quick glance at the airspeed triggers a knee jerk reaction: lower the nose! Whoa! The ground is coming up fast: raise the nose! By now the sink rate is high and the airspeed is even lower! Can the landing be saved by elevator alone? Unlikely! Mother nature and panic yankin and crankin have robbed the airplane of the necessary kinetic energy needed for a controlled flare! The only trick left in the bag is POWER! Immediate and significant power, not just an extra hundred RPM. By now the CFI's pulse rate has doubled and his/her hand has already beat the student to the draw.
Realistically, Lear Jet drivers seldom have to think about wind gradient. But to those of us driving around in 100 mph bug smashers wind gradient, or more properly, ignorance of wind gradient could ruin a good day of flying. What's the lesson here? When making slow steep approaches such as for a short field landing be alert for a sudden drop in airspeed just as you get down to the flare zone and take one hand off the yoke an put it on the throttle. In addition, trees and buildings near the runway can cause a "wind shadow" effect. More than once I have noticed this effect when landing on runway 31 at West Bend during winds from the southwest. Short grass strips are sometimes carved out of the woods and are especially prone to this nasty surprise on windy days! So maybe that platitude about carrying and extra 5 to 10 knots isn't so silly after all!
Last edited by wheels up; 15th Sep 2004 at 13:06.
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Wheelie
Calm down - you are far too tense - I was actually agreeing with you - especially wrt rotor effect. Any PPL in the S.Hemisphere should know that as you climb after take off the wind will increase and back! (veer in the N.H!) Probably why I have moved on from pistons doing 100mph - about getting hurt , don't tempt fate- but hey never say never, roll on retirement!!
Calm down - you are far too tense - I was actually agreeing with you - especially wrt rotor effect. Any PPL in the S.Hemisphere should know that as you climb after take off the wind will increase and back! (veer in the N.H!) Probably why I have moved on from pistons doing 100mph - about getting hurt , don't tempt fate- but hey never say never, roll on retirement!!
