Interesting winds at CYTZ today

[photofly]

Surface winds: 090 at 8kts

Right circuits in use on 08.

Wind at circuit altitude: 240 at 35kts, pretty much constant down to 200agl. I was flying downwinds at 95kts TAS with a groundspeed as reported by Tower of 60kts. Also crabbed about 30-40 degrees away from the runway with a terrific tailwind on the base leg.

I did one go-around, watched Porter going around too, then heard on the hand-held, after shutting down, that Tower had decided to switch runways to 26. So that would be about 40 kts of windshear (loss of headwind) between 200 agl and the surface. I don't think that would be a lot of fun.

[Colonel Sanders]

pdw was right!

First Colorado, then the Island.

Zounds.

[pdw]

Ohh the ISLAND ... nothing at all like being among those Colorado Mountains on a very windy day. Yet here you have nearly calm cold (stable) air moving opposite under some high winds, unique partly because lower Lake Ontario where CYTZ is located lies 300ft lower than Erie, on this day just upwind to the southwest (the higher Escarpment in between); definitely no mountains there to 'mix it up'.

In contemplating a suitable comparison, this "interesting winds" scenario is perhaps something like what went on during a real bad accident on Erie in the winter of 2004 (not too distant memory/ CYPT) somewhat alike to this CYTZ anomaly. Perhaps not as strong above, the takeoff winds in that case were 6kts from one direction, 90 degrees left Xwind give or take, yet not too high above the treetops was the 'strengthening downwind with height' on the PIC's chosen direction / climb path ...

Interesting too, at CYTZ there is a delicate point highlighted ... that there's the decision to switch the runway from 08 to 26 which may otherwise have seemed unnecessary when JUST looking at surface windsock; but ATC makes that happen early by noticing the ridiculous groundspeeds on various legs. ie: Was there a chance to practice "5 knots" Photofly ? Now with the tailwind touch and go you'd be facing quite the relative-wind increase on the upwind leg ... not being the case if ATC unaware of a bad increasing tailwind in climbout / on ILS/GS.

Wondering about what that OAT would have been like at CYTZ circuit height or 2K ... 3K ? The surface only 6-7C ... it must have been progressively warmer up there with-in the steep temperature gradient.

Just 32NM south, near CYSN, (our) winds at the same time "today" were 25kts at 24 C (the same airmass).

The chilling air layering over Lake Ontario's 5deg water around CYTZ was resisting retreat against very warm southwest airflow in a SW/NE-aligned trough moving into the area from the west. "8kts at 090" below "200ft" is that extra-cold air stratifying/levelling down over the water at the west-end lake-head, while also being ushered westward via a lowering atmospheric pressure from east to west across the lake surface and into that LO-trough approaching.

CS it's true the in depth analysis seen with the "33kts" in Colorado or an unusual shear event that gets highlighted at CYTZ can offer some decent insight into the workings of these types of weather products contouring the terrain at hand ... so the experience varies in each area; yet the actual WX-systems crossing the landscape are no different to what's experienced regularly by aviation generally / everywhere.

[pdw]

Wind at circuit altitude: 240 at 35kts, pretty much constant down to 200agl. I was flying downwinds at 95kts TAS with a groundspeed as reported by Tower of 60kts. Also crabbed about 30-40 degrees away from the runway with a terrific tailwind on the base leg.

I did one go-around, watched Porter going around too, then heard on the hand-held, after shutting down, that Tower had decided to switch runways to 26. So that would be about 40 kts of windshear (loss of headwind) between 200 agl and the surface. I don't think that would be a lot of fun.

The change to 26 (090@8kts/surface and 240@35kts/above-200ftAGL):

Left base 26 in honking downwind would make it the real wide turn (a real turn-illusion there likely) still with the same base-leg tailwind. Now turning final 26 slows down to a snail ground-speed with a steep descent down up-to "200ft". Between 200 and the flare, groundspeed now must rise above your airspeed which forces a shallowing descent angle, with a substantial momentum-gain required there (but that's no problem for the lighter arrival-aircraft).

In the takeoff roll groundspeed would remain above airspeed linearly up to rotation then slowing greatly again (less than airspeed) in process of passing that "200ft" mark ... facing into an extra 35kts above that height. Therefore the upwind leg gets the very steep (desireable) climb angle after "200ft", the safe thing to do for heavy departures (heaviest loaded).

[photofly]

In a Cessna:

Climbing into an increasing tailwind: lousy climb rate
Climbing into an increasing headwind: fabulous climb rate

Descending out of a decreasing tailwind: you're going to end up high on approach. I guess that applies to Q400's, too.Here are some of the CADORS from Porter's go-arounds:

2014O720
2014O726

[Aviatard]

Climbing into an increasing tailwind: lousy climb rate
Climbing into an increasing headwind: fabulous climb rate

Rate usually implies something per unit of time, so climb rate would be unaffected, no? However, I can see that your angle of climb would be lousy or fabulous, depending.

I know, it's nit picking. I have nothing better to do.

[photofly]

Climbing into an increasing headwind: the increasing airflow does work on (imparts energy to) the aircraft and does truly increase its rate of climb.

Into a decreasing headwind, vice versa.

Birds, glider pilots and model aircraft enthusiasts can all exploit a vertical wind gradient as a power source: http://en.wikipedia.org/wiki/Dynamic_soaring

Sometimes, after takeoff, you find that your aircraft is climbing "really well" - more than usual - rate wise. That's a sure sign you're climbing into a strong increase in headwind. Climbing into the strong tailwind layer at CYTZ the other day my rate of climb was significantly less than usual- same aircraft, load, temperature, and airspeed. That was because of the rapidly increasing tailwind on the climb out.

[pdw]

...rate of climb was significantly less than usual- same aircraft, load, temperature, and airspeed.

... runway 08 departure.

The westerly wind / 35kts tailwind above "200ft" is close proximity to the threshold for the larger aircraft arriving on 08 glide-slope, as is the reduced "rate of climb" phase of this departure (in the quote). Not a real surprise then to see the unavoidable overshot approaches.

After an active switch to 08-reciprocal / rwy-26 the approaches are at the same end as previously the departures, where below "200ft" on short-final the 'incoming' now experience a significantly reduced descent angle when into the increased-GS / diminishing headwind component, which needs compensating power. The rate of descent might not change though where the slope wants to go flat (add the power) after "200ft", seeing the aircraft needs to get faster there for airspeed maintained. Unlike in the 08 take-off description the descent has all excess power available to correct any shear decay of descent airspeed quickly while dropping out-of 240@35kts headwind-component to the 090@5kts light tailwind down at the 26 numbers.

Managing momentum while approaching 08 would be challenging when slowing-up on the glide-slope down from the 35kts (tail) and already so near to the runway threshold. The opposite approach manages to the numbers with ease, with as much power available as needed, while also having great climb-rate in the departure at maximum power (no excess available there). For any negative runway headwind, extra force (engine or braking energy) is needed to accelerate / stop, and a need to expect how much more (ie in a nominal power take-off) which all depends on speed of the tailwind.

[shimmydampner]

Climbing into an increasing headwind: the increasing airflow does work on (imparts energy to) the aircraft and does truly increase its rate of climb.

Into a decreasing headwind, vice versa.

Birds, glider pilots and model aircraft enthusiasts can all exploit a vertical wind gradient as a power source: http://en.wikipedia.org/wiki/Dynamic_soaring

Could you elucidate exactly how this works for simpletons like myself? Isn't a change in airflow essentially a change in airspeed which would be managed by the pilot to maintain Vy? And, all other things being equal, shouldn't climb rate at Vy be the same whether I'm climbing into 10 kts or 40? Your Wikipedia link, while interesting, only discusses changes in airspeed and groundspeed making no mention of rate of climb.

[photofly]

to maintain Vy? And, all other things being equal, shouldn't climb rate at Vy be the same whether I'm climbing into 10 kts or 40?

In an example vertical wind gradient, you're climbing into a headwind that's 10kts, then 11kts, then 12, then 13, then 14 until at some altitude the wind stops increasing as you climb. A constant headwind doesn't affect your rate of climb; but here the aircraft experiences an increasing headwind, which does.

Let's say your rate of climb is 10 feet per second, and the headwind increases 1kt with every 10 feet of climb. you experience a headwind that increases at 1kt/second. While maintaining Vy you now find that you're climbing at a rate that would -absent the wind gradient- cause the aircraft to lose airspeed at 1kt/s, yet due to the increasing headwind the airspeed remains constant.

Climbing into an increasing tailwind while maintaining a constant indicated airspeed, the aircraft has to accelerate forwards to make up for the loss of headwind. That acceleration requires power, which is no longer available to raise the aircraft against gravity: the rate of climb is reduced.

Your Wikipedia link, while interesting, only discusses changes in airspeed and groundspeed making no mention of rate of climb.

A source of energy is a source of energy: I can use it either to go faster or climb faster. Of course, since the energy source is a windshear layer at a fixed altitude, I can only use it to climb faster once: once I've climbed past it I can't use it to climb further.


Is that any clearer?

[PilotDAR]

Is that any clearer?

Not so much for me. I would agree that a gust headwind can be momentarily harnessed for "energy" into the aircraft, and will momentarily improve performance, but my experience has been that this can also be associated with a lull in a gust, which can negate the gain.

I opine that an increase in headwind, which does not act against the inertia of the aircraft, does not increase the energy into the aircraft, and cannot be harnessed for additional performance. Gusts aside, the only energy in my plane comes from the gasoline, which I convert into thrust. Whether climbing, or in level flight, a change in sustained wind does not affect my available energy.

A steady headwind increase will not result in an increase in indicated airspeed in cruise, so I can't see how it could result in an increase in climb rate (in altitude verses time) either..... You just get a slower groundspeed and lesser range - your airspeed and endurance (your total energy) remain the same, regardless of steady windspeed.

[pdw]

10kts headwind on the take-off roll.

A normal take-off might expect as much as 15 or 20kts headwind by 200ft, but instead it's now a -30kt headwind.

But lets just take those "10kts" of expected headwind, ie when no relative wind increase at all is expected in early climb.

Now subtract minus 30kts headwind, the tailwind here at 200ftAGL (departing 08 at the time).

So 40kts of momentum goes missing there.

To rebuild that 40kts momentum right there is only possible by keeping climb airspeed steady by lowering the climb-angle pitch axis and wait for the power to let ground speed build from 60kts to 100kts as the airframe cuts into the increasing tailwind of the downwind layer. My estimation is that a correction in climb-rate would take about the same power to accomplish as it took for launching the aircraft down the runway from the starting airspeed of 10kts until about 50kts of airspeed, the same 40kts of difference at the same climb power.

That's a fair bit of time at full power, about 15-20 seconds at least ..the power it would take to uphold your expected climb-rate there if you didn't know the shear was there. Cutting through that much shear difference in only 10 seconds would be double or triple the applied power required, unless flattening the climb angle early and taking some extra time to do so. I suspect to hold steady airspeed any smaller aircraft at M.T.O.W. would have needed a zero climb rate for at least that long, through the center of this strength of shear transition.

[pdw]

Is that any clearer?

Not so much for me. I would agree that a gust headwind can be momentarily harnessed for "energy" into the aircraft, and will momentarily improve performance, but my experience has been that this can also be associated with a lull in a gust, which can negate the gain.

I opine that an increase in headwind, which does not act against the inertia of the aircraft, does not increase the energy into the aircraft, and cannot be harnessed for additional performance. Gusts aside, the only energy in my plane comes from the gasoline, which I convert into thrust. Whether climbing, or in level flight, a change in sustained wind does not affect my available energy.

A steady headwind increase will not result in an increase in indicated airspeed in cruise, so I can't see how it could result in an increase in climb rate (in altitude verses time) either..... You just get a slower groundspeed and lesser range - your airspeed and endurance (your total energy) remain the same, regardless of steady windspeed.

When the light aircraft on a taxiway is not moving with brakes released, or a float plane stopped on the water, is affected by a sudden 40kt relative surface wind whether front or back it takes a while to accelerate it that direction with any significant speed ... 10 - 20 seconds sometimes to catch up to the faster wind-speed. Grant it, the airflow across the airborne wing surfaces is more attached to the airmass; yet the momentum of the airborne aircraft will also respond with delay to any such change. During that delay is where climb rate is affected positively or negatively. The delay might be 10 seconds or 30 seconds for the aircraft's momentum energy to adjust, depending how sharp an increase or decrease is experienced at the shear transition.

In cruise your airspeed will drop just little too when meeting a new wind component as tailwind component, but you might not notice a 1 or 2 knot IAS decrease for 20 seconds at that speed and rpm except that your GPS will very gently show the increase in ground-speed which can be a bit surprising if you're watching a strong change. Can't really tell the change of rpm in the engine there either, however if the prop cuts into the tailwind air (slightly slowing rpm) the piston engine will labor just a bit more and thereby drop just a little extra torque and power onto the airframe during that time.

Here in the CYTZ 08 headwind-reducing/tailwind-increasing climb-out example we are talking a serious nose-lowering experience at the "200ft" mark, experiencing a near zero climb-rate during a period where under normal circumstances would have climbed another 300-500feet in altitude during those 20-30 seconds of flattened climb-angle, but instead probably covered only about 200meters extra in forward distance as the groundspeed/momentum increased to around 100kts in that flat portion of climb phase.

[PilotDAR]

Hmmm, If we're talking a gust or very sudden direction/intensity change from windshear, then I agree that performance will me momentarily altered, though to me, 20-30 seconds is unrepresentativly long duration for this, 5 seconds maybe.

But a "normal" rate of windspeed change, would not result in a noticeable affect on performance, other than that measured relative to the surface of the earth.

A gust can pick up an aircraft from the surface, only because the aircraft has the momentum of being on the surface, and the gust reperesents a sudden change to that.

[trey kule]

In the OP , I noted he specified increasing and decreasing in the wind...and apparently enough to be noticeable.

It almost seemed to me that it was pulled from a theoretical textbook. The key here is that the wind is neither steady or gusty. Something that I dont really recall encountering. Wind shear is usually a bit more violent than that.

I am impressed that a pilot flying circuits in a small plane could notice the climb rate performance differences. Particularly as the op. Said it was a Cessna. Share with us, if you will what the difference was. Normal at the density alt ...with an increasing wind, decreasing etc.

When we studied dealing with microbursts it was because of the gust factor and its immediate effect on the plane. but once the plane adjusted, no one mentioneda climb performance issue due to wind speed changes. Vertical direction , yes.,so I expect that the unusual situation of a constant increase or decrease is the issue...

[pdw]

If we're talking a gust or very sudden direction/intensity change from windshear, then I agree that performance will me momentarily altered, though to me, 20-30 seconds is unrepresentativly long duration for this, 5 seconds maybe.

Cutting up through that transition with your climb flightpath doing "10kts" headwind at the surface to 30kts tailwind component (40kts negative) by 300ftAGL would require a 1kt per second groundspeed increase if it takes 40seconds to reach the other side, 2kts if that takes 20seconds.

Reaching 60kts of ground-speed during a typical take-off roll; say 30 seconds full power would be an acceleration of 2kts per second, ... if reached in 20 seconds is 3kts per second.

A gust can pick up an aircraft from the surface, only because the aircraft has the momentum of being on the surface, and the gust reperesents a sudden change to that.

I was just referring to the extra wind-strength moving the airframe ... the surface gale must be strong enough to even move those stationary aircraft, but then it takes a few seconds to set the airframes in motion (ie to roll away or float away) to catch up to the constant speed of that new wind.

Similarily it must be that an airframe that is crossing an intense shear transition suddenly enters the opposite direction air (listed above) slows or speeds to that windspeed over some time, not necessarily only 5 seconds ...

I could be missing something ...

[photofly]

In the OP , I noted he specified increasing and decreasing in the wind...and apparently enough to be noticeable.

Are you kidding? A 35 knot headwind in the downwind, to a 9 knot reported headwind down the runway, the other direction? You'd have to have your eyes clamped shut to miss it. And you don't think that's going to affect your aircraft performance as you change altitude? Really?

Let's look at the CADORS from the Porter flights that had to go around. I personally watched two go-arounds by Porter Q400s while I was in the circuit - one on the Sunday and one on Monday. Those pilots are good, and they don't go around unless something is amiss.

Quartering 40kt southwest tailwinds down to 250AGL, surface winds from East 7kts. A Porter Airlines de Havilland DHC 8 402 (C-GLQM/ POE682) from Sault Ste Marie, ON (CYAM) to Toronto/ Billy Bishop, ON (CYTZ) elected to go-around.

Strong (~40kts) southwest winds aloft above 250AGL, surface wind speed (SFC) SW 6kts. A Porter Airlines de Havilland DHC 8 402 (C-GLQP/ POE250) from Ottawa, ON (CYOW) to Toronto/ Billy Bishop, ON (CYTZ) elected to go-around, landed 1440Z.

It continued the day I posted, and the day after (Monday, I think): here's the Monday morning TAF:

TAF CYTZ 141342Z 1414/1514 00000KT WS010/20035KT P6SM BKN180 FM141600
19012KT P6SM SCT050 OVC150 FM141800 22015G25KT P6SM -SHRA
OVC040 FM142000 22015G25KT P6SM -SHRA OVC020

I'm sorry you haven't experienced it, or that you're surprised a pilot of a light aircraft might notice his or her climb performance. I recommend you get more in tune to what your airplane is trying to tell you as it flies - it might make you a better pilot.

Share with us, if you will what the difference was. Normal at the density alt ...with an increasing wind, decreasing etc.

That day, on the climbout from 08 from the headwind into the south-west tailwind, rate of climb, at Vy was about 200fpm. Normally about 600fpm. If we'd departed 26 with a tailwind on the ground into the 40kt headwind at 250ft, I'd expect a rate of climb about 1000fpm+, through the windshear layer.

Here in the CYTZ 08 headwind-reducing/tailwind-increasing climb-out example we are talking a serious nose-lowering experience at the "200ft" mark

Yep, that's exactly right. Had to lower the nose significantly below the normal climb-out attitude to maintain Vy, and got a horrible rate of climb. However the wind was so strong you could feel it accelerate hard over the water.

[photofly]

Hmmm, If we're talking a gust or very sudden direction/intensity change from windshear, then I agree that performance will me momentarily altered, though to me, 20-30 seconds is unrepresentativly long duration for this, 5 seconds maybe.

You're stuck in a mindset that says windshear is all about gusts - winds that vary in time, and not considering how the wind can be significantly different with very small changes of altitude. Smoothly, and for a period of at least 24 hours, in this case. It's unusual, but not unprecedented at CYTZ: I remember it being the case on at least two other occasions in the last couple of years.

How long does it take an aircraft to climb 200 feet, and what will the aircraft do if the headwind or tailwind changes by 40kts over this flightpath and that period of time?

[pdw]

The key here is that the wind is neither steady or gusty. Something that I dont really recall encountering. Wind shear is usually a bit more violent than that.

It definitely looks steady as it shows there ... as presented now in the Cadors exerpts. A normal climb path would go thru this transition's height probably in the first 15-25 seconds of climb, except the minimum airspeed can't let this happen when the pilot must lower the nose substantially as he's maintaining it.

I am impressed that a pilot flying circuits in a small plane could notice the climb rate performance differences.

It was the tower that brought some of that detail to his attention ....

[photofly]

I am impressed that a pilot flying circuits in a small plane could notice the climb rate performance differences.

It was the tower that brought some of that detail to his attention .... which is not always the case

Thanks, but I don't need the tower to tell me that my groundspeed on downwind is half what it usually is. Or that in order to avoid being blown towards the threshold at 40kts I have to crab 30 degrees away from the runway all the way down the base leg. Any pilot experiencing that then looking at the windsock sticking out straight down the runway would know the wind was going to shear significantly on short final.

More generally:

If, at any airport, the surface winds are 5kts, the winds at 500ft are almost always going to be stronger. Since you always (*) take off into the wind, you're almost always going to be taking off into an increasing headwind. So you always get a boost to your rate of climb, even if it's too small for the unobservant to notice.

Compare your rate of climb on a windy day, vs on a still day. The windy day will win, even if not by much - because the headwind increases with altitude - and therefore increases with time as you climb out.