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Plane flips over after crash-landing in Somalia

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Plane flips over after crash-landing in Somalia

Old 27th Jul 2022, 19:56
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Only if you are looking at ground speed, not airspeed. A tailwind will make you land long.

Me
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Old 30th Jul 2022, 06:25
  #22 (permalink)  
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Originally Posted by ItsonlyMeagain View Post
Only if you are looking at ground speed, not airspeed. A tailwind will make you land long.

Me
er, why?
¿por qué?
sei?
mengapa?
なぜ?
لماذا ا؟
waarom?
perché?
Varför?
ทำไม
tại sao?

How does a tailwind affect the aiming point which is determined as a geometric point on the runway, and to which in general a vertical path is expected to be flown to intercept the same point?
If the statement refers to the rollout due to the higher groundspeed, then that is different.

just curious

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Old 30th Jul 2022, 07:00
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You are correct that a 3 degree flight path with a fixed aiming point is fixed in space; I did not dispute that. However to maintain that with any wind, the variable is power. In a strong tailwind there will come a point where this is not possible as the power will be at idle. Of course, the way to maintain the flight path now is to point at the aiming point as the tailwind tries to put you above the profile. Should one arrive at the aiming point at the correct height, you will certainly be fast and….. you will land long. Professional pilots call this an unstable approach.

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Old 30th Jul 2022, 08:08
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Originally Posted by fdr View Post
er, why?
¿por qué?
sei?
mengapa?
なぜ?
لماذا ا؟
waarom?
perché?
Varför?
ทำไม
tại sao?

How does a tailwind affect the aiming point which is determined as a geometric point on the runway, and to which in general a vertical path is expected to be flown to intercept the same point?
If the statement refers to the rollout due to the higher groundspeed, then that is different.

just curious
A headwind, reducing close to the ground, will let you drop out of the air due to insufficient airspeed, whereas a tailwind, reducing close to the ground, will increase the airspeed and as such, keeps you flying/floating longer, IE your landing spot automatically moves further down the runway.
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Old 30th Jul 2022, 23:13
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Originally Posted by WideScreen View Post
A headwind, reducing close to the ground, will let you drop out of the air due to insufficient airspeed, whereas a tailwind, reducing close to the ground, will increase the airspeed and as such, keeps you flying/floating longer, IE your landing spot automatically moves further down the runway.
The dynamics of a shear associated with the turbulent boundary layer is quite straightforward, but the aiming point is the aiming point, and the flare/ thrust reduction is a process that is trained and mastered by the pilot in qualification. A rollout will be extended by the higher ground speed, nut nothing in Part 25 Subpart B lets the pilot off the hook for not being able to fly a path to an aiming point, flare/reduce power at an appropriate time and land.

In simple terms an into wind landing has an undershoot shear where the wind component reduces due to the TBL approaching the ground. Response is a pitch adjustment and thrust change while transiting the shear to maintain parameters. The immediate change is a reduction in IAS from inertial factors, while groundspeed increases... speed stability results in the attitude naturally lowering which matches the higher sink rate rest for the higher ground speed. Once sterilised conditions occur, thrust and pitch change to maintain the higher sink condition for a geometric glide path.

For the tailwind case, indeed the handling is more fun; the reducing tailwind in the TBL gives an inertial effect of an increase in IAS, which gives arose up moment from speed (alpha) stability), the GS reduces so the required VS for the geometric path then requires IAS to be stabilised, thrust initially comes off but then has to be set at slightly higher levels than that required prior to the shear.... and the stable conditions attained. It is an overshoot shear, and is one of the reasons that for high inertia aircraft like the 747/777/380 etc reference ground speed or GSmini was a nice briefing item, it gets a target in mind as to what is going to be the processes for the maintenance of a stable path.

The requirement is still to maintain a path, and to arrive at the flare point with the correct energy state, so my query stands. Are we saying that pilot training is inadequate to fly an aircraft within normal criteria for a stable approach?

In respect to this bingle, the LH MLG has impacted soft ground prior to the lip of the runway hard surface, which is commonly called landing short. If the premise is that in order to not land long on a landing with a tailwind, instead we ens up with landing short, effectively having a ramp strike, then we seem to have other problems. As a simple horizontal shear to cause an outcome like that in a closed loop control system would be an instantaneous loss of the 0.3 amount of the 1.3Vs that Is being applied on the reference speed, or a sudden/instantaneous loss of 25kts of tailwind component. That being the reason to have some inkling of GSmini (lé Busse), RGS (Billie Boing) etc... For low inertia aircraft, the effects are less pronounced, but mechanical turbulence can be more annoying.

Still, Fokker made a solid tube, plane handled that bingle rather well.

Last edited by fdr; 31st Jul 2022 at 04:55. Reason: Gemini, I hate auto spell
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Old 31st Jul 2022, 03:48
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Finally some sense !!
sticking the MLG into the sand short of the concrete will in most cases be detrimental to it's health.
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Old 31st Jul 2022, 03:58
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Originally Posted by ItsonlyMeagain View Post
You are correct that a 3 degree flight path with a fixed aiming point is fixed in space; I did not dispute that. However to maintain that with any wind, the variable is power. In a strong tailwind there will come a point where this is not possible as the power will be at idle. Of course, the way to maintain the flight path now is to point at the aiming point as the tailwind tries to put you above the profile. Should one arrive at the aiming point at the correct height, you will certainly be fast and….. you will land long. Professional pilots call this an unstable approach.

Me
Me; the effects of inertia means that IAS is affected unless the "shear" (change/time) changes are very slow rate, and/or the aircraft has low inertia. Within an airmass, the aircraft is moving but takes time to accelerate the inertial mass, so the GS does not instantaneously increase by 50kts in a sudden 50kt reducing headwind, instead, the IAS (CAS) alters immediately, it is not subject to inertia, and the ground speed alters rapidly but not instantaneously until reaching equilibrium (turning a B747 to the NE over Kushimoto with a 250kt jet stream, where the component would go from a 100kt head to about 250 tail was always worth a bet for the first beer in Narita, a 350kt shear in 45 seconds was always worth watching). Slow rates, no problem light planes, no problem.

Re "power is the variable", that is not the issue with most reverse shear cases. The attitude has to change as the first effect of the drop off of a tailwind is an increase in IAS, that causes a pitch up if open loop control due to speed stability. That acts to reduce sink rate, while at the same time, the rapidly increasing ground speed now necessitates an increase in sink rate, so the immediate effect open loop is to go above glide slope. Closed loop, the pilot has to add a nose down input to avoid the balloon from the additional IAS increment, which also needs further adjustment due to the increased sink rate requirement over time as GS increases to equilibrium condition. The increased speed requires a power reduction, (first power change, more to come). As the conditions stabilise, the IAS starts to reduce other than the increment that occurs from the lower attitude required for the higher sink rate, which then requires an addition of thrust to stabilise back at the equilibrium condition, which hopefully is back at Vref + additive, and with the power slightly lower than prior to shear entry, and with a slightly lower attitude to maintain path. The problems arise when the crew carry excess speed into a reverse shear, and cannot get the aircraft to return in time to stable conditions in order to be stable into the flare. Stable here is still within the generic requirements for a stable approach that companies will specify in their OM's.... The routine problem from the investigators view is to determine whether the crews actions were within normal boundaries for the conditions. Carrying excess speed into a reverse shear is a headline that the crew are not cognisant of the dynamics that will occur (the opposite is true for a normal shear event). A ballooning out of the slot during transition of a reverse shear is indicative of the crew not adjusting the attitude for the speed change, excess IAS correlates to inadequate thrust reduction during the transition; low IAS/energy into the flare is indicative of failure to restore thrust before the flare... A factor that often shows up on hard landing investigation is that the crew take the power off due to the excess IAS, and then do not add it back to somewhere near a normal thrust level before entry into the flare...

All of this takes more time to say than do.... but the sequences of actions are constants, and show deviations from desired controlled state.

Tin hat time.... the B767 that was climbing at idle as it entered a spectacular shear from the jet wind... climbing at MMO with speed brake out and thrust at idle. Impressive.
Or the B737-800W that missed its level off by 4000' going up, with a 1.72g pull up, a 0.2g over the top, and the subsequent 1.7g pull to level off at the assigned altitude. All at idle and with the speed brake out, at MMO. Neat jet stream.

All of the above barely rises above the point of boredom, but if the driver starts briefing about adding speed for mum and the kids for an expected reverse shear, then it is apparent they don't comprehend what the aircraft does in shears. We get the unfortunate lot to be presented with interesting conditions that appreciate preparation, and occasionally a rational "er, no thanks, I'll take the other runway...". As a group, we routinely try harder than we should to accomodate lunacy arising from bureaucracy, and the outcome occasionally is a desire to have a repeat of the last 10 seconds again while sitting in the wreckage.

This may seem like teaching to suck eggs, but the number of pretty shambolic approaches that get analysed suggests that we can occasionally do with clearing our thoughts. For the non flying driver, it is even more important that he or she understands what is going to happen next. The side kick doesn't have the input of the control feel to include in the process so can only rely on the performance gauges and comprehension of "plain fiziks" to be inside of the loop in a meaningful manner. In the really ugly events that come across the desk, the data shows frequently around 4-5 seconds of prior deterioration of flight kinematics before the day gets mussed up. (slightly less I guess for the Mega Deaf II, if I recall correctly).

The wise words of Mme 'Bussé and Mr Boing for all of their shiny toys invariably indicate that thrust is one of the factors in determining whether stable or not, and almost every nasty landing that I have had to analyse had the thrust well away from a normal fist position crossing the threshold. Being at idle already or TOGA thrust at that point may result in expenses. (results may vary...)

Last edited by fdr; 31st Jul 2022 at 05:07.
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Old 31st Jul 2022, 06:48
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Well, apart from tin hat, boredom and suck eggs, I didn’t understand any of that. However, I now know how to ask why in an additional 10 languages.

I have always found teaching people in language and at a rate they could understand produces sound results.

I guess none of your explanations were going through the pilot’s head as he hit the undershoot.

Me
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Old 31st Jul 2022, 15:15
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In plain language.

I have flown into Mogadishu on many many occasions, and certainly it can be interesting.

Tailwind is either within limits, or out of limits in which case the flight diverts, or is cancelled.

The runway is very long, which rather begs the question what an F50 was doing with its MLG

in the undershoot of a very long runway on a pretty average day?

It makes no sense, these things were daily in and out of LCY, without issues.


TR
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Old 1st Aug 2022, 04:39
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Originally Posted by Teddy Robinson View Post
I have flown into Mogadishu on many many occasions, and certainly it can be interesting.

Tailwind is either within limits, or out of limits in which case the flight diverts, or is cancelled.

The runway is very long, which rather begs the question what an F50 was doing with its MLG

in the undershoot of a very long runway on a pretty average day?

It makes no sense, these things were daily in and out of LCY, without issues.


TR
Sorry, I oversaw the base leg approach with short final for MGQ.

I don't think, this was an "undershoot".

When there is a landing tailwind of (for example) 20kts, and one does approach on the base leg with 90kts (both airspeed and ground speed), as fdr writes, you'll need military jet performance to pick up the kinetic energy to stay on 90kts airspeed and reach 110kts ground speed. Don't have an acceleration and your airspeed will effectively become 70kts, and (you'll) subsequently drop out of the sky (or at least your margins get tight).

Not to say, because of the (tight) turn to final, your stall speed goes up significantly, the decreasing from 90kts airspeed is no longer enough to fly and your inside turn wing will start to drop. That'll start to happen somewhere half-way your turn to final. Depending on the speeds/situation, you end up nose-down, or just somewhere halfway flipping over and ending up trying to land on the wingtip. Depending on how far your flip did go (before or already through the vertical), you end up with just scraping the wingtip, an extreme hard landing on one MLG (breaking off the whole wing on that side) or just landing upside down. When your wing breaks off, you'll end up upside down, since the other wing still wants to fly (creating a fuselage rotating force, even when the wing is vertical).

The final location off the right side of the beginning of the runway corresponds with the flying direction when the in-turn wing starts to stall somewhere during the turn to final. For this situation, it looks like the wing broke off due to an extreme hard landing, with a subsequent flip-over.

So, no landing gear issues, or an undershoot or so, just a (marginal) in-turn stall. Which fortunately left the fuselage intact and all survived.
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Old 1st Aug 2022, 05:48
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Seek and you will find

There is a video taken from adjacent to the runway 05 threshold.
Enter one F50 right to left, left wing down, nose pitched slightly up.
Left main gear strikes start of prepared surface followed immediately by failure of the left wing structure.
I would call that fairly conclusive.

Missed approach for 05 is a gentle right turn to avoid overflying the port area to rejoin either the visual circuit, or RNP to visual depending on other traffic and ATC.

TR

Last edited by Teddy Robinson; 1st Aug 2022 at 05:50. Reason: typo
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Old 1st Aug 2022, 13:48
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Why can't you be bothered to provide a link? The only one I could find.


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Old 1st Aug 2022, 15:45
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Sorry, I was rather busy today.

The second of those clips is taken from the area just north of the 05 threshold
This is the clip that I am referring to.

Note: the aircraft has touched down hard in the undershoot, by 3rd second of the clip the wing has failed and the left engine is pointing towards the tarmac .... and the rest as they say is history.

Last edited by Teddy Robinson; 1st Aug 2022 at 15:48. Reason: typo
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Old 1st Aug 2022, 18:00
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Originally Posted by WideScreen View Post
Sorry, I oversaw the base leg approach with short final for MGQ.

I don't think, this was an "undershoot".

When there is a landing tailwind of (for example) 20kts, and one does approach on the base leg with 90kts (both airspeed and ground speed), as fdr writes, you'll need military jet performance to pick up the kinetic energy to stay on 90kts airspeed and reach 110kts ground speed. Don't have an acceleration and your airspeed will effectively become 70kts, and (you'll) subsequently drop out of the sky (or at least your margins get tight).

Not to say, because of the (tight) turn to final, your stall speed goes up significantly, the decreasing from 90kts airspeed is no longer enough to fly and your inside turn wing will start to drop. That'll start to happen somewhere half-way your turn to final. Depending on the speeds/situation, you end up nose-down, or just somewhere halfway flipping over and ending up trying to land on the wingtip. Depending on how far your flip did go (before or already through the vertical), you end up with just scraping the wingtip, an extreme hard landing on one MLG (breaking off the whole wing on that side) or just landing upside down. When your wing breaks off, you'll end up upside down, since the other wing still wants to fly (creating a fuselage rotating force, even when the wing is vertical).

The final location off the right side of the beginning of the runway corresponds with the flying direction when the in-turn wing starts to stall somewhere during the turn to final. For this situation, it looks like the wing broke off due to an extreme hard landing, with a subsequent flip-over.

So, no landing gear issues, or an undershoot or so, just a (marginal) in-turn stall. Which fortunately left the fuselage intact and all survived.
I'm sorry, WHAT?? Airplanes do not fly relative to the ground, they fly relative to the air. If you fly an airplane at 60kts, against a 60kts headwind, you will be stationary over the ground, but you will not stall. If you make a 180 degree turn your groundspeed will now be 120 kts, but you will not exceed any aircraft speed limit. This applies in the patterns as well. If you are on the base leg and you have a headwind for landing, your turn to final will be a bit less than 90 degrees, due to the crab angle on base. Conversely, if you are landing with a tailwind your turn to final will be bigger that 90 degrees. If your approach speed is 90 kts, and you turn final in either cease, your indicated speed will (should) stay at 90 kts. Your ground speed will go up for a tailwind and down for a headwind, but your airplane wont realize that, because it's only reference is the air around it. I cannot believe there are pilots that think aerodynamics are affected by ground speed. Yes, landing distances are. Yes turn radiuses across the ground are. YOU WILL NOT LOSE AIRSPEED TURNING INTO A "TAILWIND".
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Old 1st Aug 2022, 18:17
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The downwind turn tale die slowly
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Old 1st Aug 2022, 18:49
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Originally Posted by hans brinker View Post
I'm sorry, WHAT?? Airplanes do not fly relative to the ground, they fly relative to the air. If you fly an airplane at 60kts, against a 60kts headwind, you will be stationary over the ground, but you will not stall. If you make a 180 degree turn your groundspeed will now be 120 kts, but you will not exceed any aircraft speed limit. This applies in the patterns as well. If you are on the base leg and you have a headwind for landing, your turn to final will be a bit less than 90 degrees, due to the crab angle on base. Conversely, if you are landing with a tailwind your turn to final will be bigger that 90 degrees. If your approach speed is 90 kts, and you turn final in either cease, your indicated speed will (should) stay at 90 kts. Your ground speed will go up for a tailwind and down for a headwind, but your airplane wont realize that, because it's only reference is the air around it. I cannot believe there are pilots that think aerodynamics are affected by ground speed. Yes, landing distances are. Yes turn radiuses across the ground are. YOU WILL NOT LOSE AIRSPEED TURNING INTO A "TAILWIND".
Maybe read again, what I wrote.....

You think in speed. That's the wrong approach. You need to think in Kinetic Energy, and that is ground reference based. When you turn final with Kinetic Energy Ek, it represents a ground speed corresponding to that Ek. And you have the same Ek on your base leg, with the same ground speed. Kinetic Energy doesn't know about airspeed. Only wings know about airspeed.

IF you need a higher ground speed to keep flying (because of a tailwind), you will need to add Kinetic Energy. If you don't do that, by pointing the nose down (trading in potential energy) and/or use engine power (trading in chemical energy), you are loosing airspeed. The extra Kinetic Energy does come from somewhere. Really.
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Old 1st Aug 2022, 19:06
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Originally Posted by megan View Post
Why can't you be bothered to provide a link? The only one I could find.

https://www.youtube.com/watch?v=P6zT0SUauu4

https://twitter.com/i/status/1552300391597047808
Looks to me, the video shows happening what I described. Though just at the end of the turn to final, where I expected this to happen a little earlier, more at 2/3 of the turn to final.

At the very first few seconds of this video, the F50 seems to be in a shallow bank to the left at the end of a turn to final. And then suddenly the F50 starts falling out of the sky, just mushing down with wobbly wings.

The turn to final with lots of tailwind on landing is really dangerous. Don't believe those fairy tales about "not loosing airspeed, when turning final". It needs positive action to avoid losing airspeed.

(And the same applies for a quick turn-out to cross-wind when taking off with a significant headwind, before you know, you are upside down.)
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Old 2nd Aug 2022, 01:05
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Megan's first video is looking in the opposite direction of the approach, and shows the aircraft was quite stable, wings level for some time before the flight path deteriorated. There is not enough resolution to have any idea of the speed, but she sure does plummet below slope there towards the end of the flight.

Hans Brinker: I cannot believe there are pilots that think aerodynamics are affected by ground speed. Yes, landing distances are. Yes turn radiuses across the ground are. YOU WILL NOT LOSE AIRSPEED TURNING INTO A "TAILWIND".
Hans... we get taught to fly light aircraft, and do stuff like ground reference manouevers in what are generally light aircraft, low inertia. Where inertia is considered to be zero, there would be no such thing as wind shear... as you say the plane only sees the air. The only difference that would arise would be a change in the flight path angle, FPA, as whatever the vertical speed, VS is relative to Ground Speed, GS, would change, FPA being VS/GS. An aircraft with inertia cannot suddenly accelerate the inertial mass instantaneously from one kinetic energy state to another, except on star trek maybe.

If you are turning into an increasing tailwind in a high inertia aircraft, you will see CAS sag and the ATR system compensate up to MCT to maintain the commanded speed. In a Boeing, that will be seen as the thrust levers moving rapidly forward, and then once the rate of change of wind (shear; dv/dt) has stabilized, and on target speed, the thrust will rapidly recover to the pre-turn levels. In an airbus, you get to see the command arcs move, the thrust values go up, then everything goes back to normal, and the crew pokemon game is undisturbed by the Boeing racket. On a B737, you also of course get the rattle of the trim system for the speed variations (there is also usually a slight trim change to maintain altitude even in calm conditions, so a clack or two is pretty normal in an extended turn on a B737).

There are two general types of wind shears that we mess about with, that related to microbursts which drivers tend to avoid wherever possible, and the common or garden horizonal shear. (There are also thermal shears, stock shares etc... ) Microbursts provide vertical and horizontal shear components that get pretty nasty quickly, and drivers tend to avoid them where possible. Horizontal shears happen every day at all altitudes, and arise from the component change to the direction of motion of the aircraft. That can be a velocity change or a vector change. If the component changes at the aircraft, there is a shear occurring.

Shear is time dependent. The driver can alter that in most cases by controlling the mode that the aircraft is controlling to. For vertical shears, (and with the ususal caveats that the driver is responsible at all times to remain within limitations and to follow company policy), traversing a vertical shear can be easily managed by using a VS mode... a nice simple 500FPM up or down is pretty darn difficult to bust a limit, or to stall the plane (but not impossible... ) a shear of 100kts in 4000' vertical is entertaining in a speed mode for climb or descent, such as FLCH, dropping out of the wind, with a reducing headwind component in FLCH will cause the plane to increase the sink rate with a pitch down to maintain speed, and the steady state sink rate will rapidly dissapear. Most memorable data I can recollect of that was a B772ER going through a 180 kt jet core, from above in a descent. Guys started the descent with the speed brake out, and the tailwind increased as they entered the core from a lower tailwind condition (taking advantage of a lower tailwind on the day.... ) so the tail wind rapidly increased, and that led to a rapid pitch down and higher sink rate... that then led to entering the airmass under the core which had a reducing tailwind component with a sink rate of greater than 12,000FPM, and a major pitch up and overspeed as the APFD wasn't nearly capable of keeping up with the rates that the driver had set up... apparently was spectacular from the inside. had the descent been done in VS at a modest rate, no ones beer would have spilled, even the pilots beer. In a modest VS, the trust would have changed to maintain the speed, and the VS would have controlled pitch. The VS compared to shear rate would have kept it boring, and boring is good. This is the reverse sort of event to the B767 commented on by me before in the climb...

For the ground reference cases, if you are zipping about the cans at Reno, even around 380CAS the rate of turn is relatively low and the winds are almost always light, so there is not much shear, and the planes are not very heavy... Doing that even in a B747 at VMO while fun would probably not give a particularly high shear rate, but it would get tea and bikkies with the boss for the overstress, or with RARA for disqualification for running off the course.

Biggest horizontal shear I ever came across was going into a VFR forecast airport, in a big twin, and noting at about 20 miles to run for a gentle turn to final that we had a northerly wind of 56kts, and the reported wind on the ground was 36kts from the south. Asked the FO who was PF to slow down early as we were going to get a pretty good shear at some point, so we configured to approach flaps, and at 1200'AGL, we still had 55kts tailwind, and 35kts in the opposite direction on the ground. Neither the ground or the upper wind were on the forecast. At 400ft the wind started to change, and the FO blew straight out of the slot with the flaps load relief getting a fair work out. As we had min fuel and no alternate, it became fun to do the final approach. It could be done, but it took controlling the rate of change to make it manageable and to land with reduced flaps. All other inbounds were diverted for the next 4 hours, and we would have too, had we had gas.

If inertia wasn't a factor, shear would not do anything other than change the VS to maintain a path, the wrecks on finals dotted around the world suggest that inertia and kinetic energy is indeed a factor, irrespective of what physics we train pilots in, akin to teaching Bernoulli's theory to explain why wings work. The oracle Google gives a number of popular science level descriptions that are completely wrong but follow the guidance that pilots get encumbered with at the start of their flying career. When DFDR data is looked at, the inertial effects can be seen in the data relatively clearly.

If this is surprising, then you should try screening out coriolis effects on jet aircraft performance data, or the variation in SAR that occurs when flying from one airmass to another. In the old days that was a pain, but with GPS geometric altitude that becomes easy to resolve, and actually ends up giving some interesting info on the actual weight/drag count, with W/delta still being a factor in the background.

If this sound pedantic or boorish, a disproportionate amount of time in DFDR QAR analysis gets used up educating ops managers that the crew were in conditions that caused changes to the flight path, and that the problem is not one of compliance it is one of awareness. That is about 37 years on that subject and it seems to have no end in sight.

Note, the reactive windshear alert algorithm is the F factor:

F=Wh G - Vd As

where:
Wh is the rate of airspeed loss in kts per seconds,
g is gravity,
Vd is the vertical down draft rate, and
As is the aircraft airspeed.

The Wh/g term represents the rate of change in the horizontal winds. The Vd/As represents a measure of down draft strength. A way to think of F-factor is the rate of removal of energy from the aircraft.


Back in the day, I suggested to the design team that the reactive alert include a +/- value rather than just a minus, as what goes up usually goes down... The predictive alert came in soon enough to be a better bet.

Stated another way...:

given the equations of motion of:


(refer the model below)





The specific energy Es becomes:



and can be expanded to:


The first component being the airplanes specific excess power, so the rest is the wind effects which is a restated F factor:








So, in the end, there are triggers for, vertical rates that arise from the vertical shear, and dCAS that comes from the horizontal shear, both items affecting the specific energy, Es, of the plane.


PS: if you want to quantify the rate of shear that your plane can encounter and not have a bit of fun, you can sit in the sim and try from a steady state in whatever configuration that you have to go to full thrust, and record the acceleration rate that you achieve. The sim will normally be within 10% or so of the specific excess thrust available, which is the thrust avaliable minus the drag. The drag curves are able to be determined to be representative by looking at the acceleration rates and rate of climb for the same weights, vs the aircraft, and the same for the approach etc, but when without that, it will be ruffly +/-10% or better in most sims that have passed QTGs.

A B747-200B has about 3.6kts/sec in landing configuration on a 3 degree slope.... so for that case, a change of component in excess of 3.6kts will result in a change of CAS. Of course the overshoot shear gets to add CAS initially, and then the driver has to deal with the speed trim change, thrust trim change, balloon, pitch, and then get the toy back to stable. Which is why the DFDR and QAR data gets to be interesting to look at when the boys have had a wobbly day out. Transition of a shear can be drawn happily on a white board, and that is the only point of this long winded comment, if the drivers can't draw the pitch, speed, thrust, trim, dGS, attitude, AOA changes that occur then there is a gap in the education, and that is systemic, not an individual failing.

Suggested reading:

Townsend, J., Low-Altitude Wind Shear and Its Hazard to Aviation, National Academy, Washington, DC, 1983.
Hinton, D. A., "Flight Management Strategies for Escape from Microburst Encounters," NASA TM-4057, Aug. 1988.
Bowles, R. L., "Reducing Windshear Risk Through Airborne Systems Technology," presented at the 17th Congress of the Intl. Council of the Aeronautical Sciences, Stockholm, Sweden, Sept. 1990.
Kupcis, E. A., "Manually Flown Windshear Recovery Technique," Proceedings of the 29th Conference on Decision and Control, Honolulu, HI Dec. 1990, pp. 758, 759.
Miele, A., "Optimal Trajectories and Guidance Trajectories for Aircraft Flight Through Windshezis" Proceedings of the 29th Conference on Decision and Control, Honolulu, HI, Dec. 1990, pp. 737-746.
Psiaki, M. L., and Stengel, R. F., "Analysis of Aircraft Control Strategies for Microburst Encounter," Journal of Guidance, Control, and Dynamics Vol. 8, No. 5, 1985, pp. 553-559
Psiaki, M. L., "Control of Flight Through Microburst Wind Shear Using Deterministic Trajectory Optimization," Ph.D. Dissertation, Princeton Univ., Princeton, NJ, 1987 (Rept. No. 1787-T)
Zhao, Y, and Bryson, A. E., "Optimal Paths Through Downbursts," Journal of Guidance, Control, and Dynamics, Vol. 13, No. 5,1990, pp. 813- 818.
Miele, A., Wang, T., and Melvin, W, "Guidance Strategies for NearOptimum Takeoff Performance in Wind Shear," Journal of Optimization Theory and Applications, Vol. 50, No. 1, 1986, pp. 1-47.
Miele, A., Wang, T., and Melvin, W., "Optimization and Gamma/Theta Guidance of Plight Trajectories in a Windshear," presented at the 15th Congress of the Intl. Council of the Aeronautical Sciences, London Sept 1986.
Morton, B. G., Elgersma, M. R., Harvey, C, and Hines, G., "Nonlinear Plying Quality Parameters Based on Dynamic Inversion," Honeywell Systems and Research Center, AFWAL-TR-87-3079, Minneapolis MN Oct 1987.
Lane, S., and Stengel, R. R, "Flight Control Using Non-Linear Inverse Dynamics," Automatica, Vol. 24, No. 4, 1988, pp. 471-483.
Menon, P. K., Badgett, M., and Walker, R., "Nonlinear Flight Test Controllers for Aircraft," Journal of Guidance, Control, and Dynamics, Vol. 10, No. 1,1987.
Meyer, G., and Cicolani, L., "Application of Nonlinear System Inverses to Automatic Flight Control Designs: System Concepts and Flight Evaluations," Theory and Application of Optimal Control in Aerospace Systems, AGARD, AG251, pp. 10.1-10.29.
Elgersma, M., and Morton, B., "Partial Inversion of Noninvertible Nonlinear Aircraft Models," Honeywell Systems Research Center, Minneapolis, MN, Aug. 1989.
Frost, W, and Bowles, R., "Wind Shear Terms in the Equations of Aircraft Motion" Journal of Aircraft, Vol. 21, No. 11, 1984, pp. 866-872
Stengel, R. P., "Course Notes for MAE 566: Aircraft Dynamics," Princeton Univ., Princeton, NJ, Jan. 1990.
Singh, S. N, and Rugh, W. J., "Decoupling in a Class of Nonlinear Systems by State Feedback," ASME Journal of Dynamic Systems, Measurement, and Control, Series G, Vol. 94, Dec. 1972, pp. 323-329.
Etkin, B., Dynamics of Atmospheric Flight, Wiley, New York, 1972
Mulgund, S. S., and Stengel, R. F, "Optimal Nonlinear Estimation for Aircraft Flight Control in Wind Shear," Proceedings of the 1994 Congress of the International Council ofAstronautical Sciences, Anaheim, CA, 1994, pp. 1747-1755.
Greene, R.A., The Effects of Low-Level Wind Shear on the Approach and Go-Around Performance of a Landing Jet Aircraft, SAE Transactions
Vol. 88, Section 3: 790527–790858 (1979), pp. 2009-2015 (7 pages)
Mulgund S.S. & Stengel, R.F.; Aircraft Flight Control in Wind Shear Using Sequential Dynamic Inversion, J. Guidance, Control & Dynamics, Vol 18, No. 5, September-October 1995.

and...

Ostroff, A. J., et al., "Evaluation of a Total Energy-Rate Sensor on a Transport Airplane," NASA TP-2212,1983.


Last edited by fdr; 2nd Aug 2022 at 03:07.
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Old 2nd Aug 2022, 05:39
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Originally Posted by WideScreen View Post
Maybe read again, what I wrote.....

You think in speed. That's the wrong approach. You need to think in Kinetic Energy, and that is ground reference based. When you turn final with Kinetic Energy Ek, it represents a ground speed corresponding to that Ek. And you have the same Ek on your base leg, with the same ground speed. Kinetic Energy doesn't know about airspeed. Only wings know about airspeed.

IF you need a higher ground speed to keep flying (because of a tailwind), you will need to add Kinetic Energy. If you don't do that, by pointing the nose down (trading in potential energy) and/or use engine power (trading in chemical energy), you are loosing airspeed. The extra Kinetic Energy does come from somewhere. Really.
I really hope you are not a pilot. You have absolutely no idea what you are talking about. Kinetic energy is not ground reference based.
When an airplane is flying around in a constant bank it will make a circle relative to the surrounding air. If that air moves across the surface of the earth the pattern across the ground will look like curly hair (sorry, don’t want to start looking for pictures). Whatever the wind is, in the airplane you will not feel any difference between turning into the wind or out of the wind. That is because your frame of reference is the air. It’s like a fly in a train. It’s not flying at a 100 mph if the train is going a 100 mph. I was going to say more, but I ran out of potential energy. (facepalm)

Last edited by hans brinker; 2nd Aug 2022 at 06:14.
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Old 2nd Aug 2022, 05:48
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Originally Posted by fdr View Post
Hans... we get taught to fly light aircraft, and do stuff like ground reference manouevers in what are generally light aircraft, low inertia. Where inertia is considered to be zero, there would be no such thing as wind shear... as you say the plane only sees the air...

Ostroff, A. J., et al., "Evaluation of a Total Energy-Rate Sensor on a Transport Airplane," NASA TP-2212,1983.
I want to clarify my statement about ground speed vs airspeed and kinetic energy was in reference to a steady wind. I was trying to keep it simple enough for widescreen, but I think that might be an impossible goal. Obviously if you descend/climb into a different wind direction or speed it will affect the performance until a new equilibrium has been reached. Even in light planes inertia isn’t zero, but that has nothing to do with the assertion that turning to final if there’s a steady state tailwind would require a power change.
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