C172 and Wind Shear

[Carson147]

Is it save to fly(and land) the C172 if there is a wind shear (almost entirely headwind) of 40 kts reported at 500ft AGL? If so, is there anything that I need to look out for when doing a power-off 180 approach?

[Heavy Rayn]

No, it’s not really safe. Look up performance decreasing wind shear. 40 knots is over half of your approach speed. Seems like an unnecessary risk in a 172, especially if you are not extremely proficient and experienced in the aircraft. As far as a P180 goes look for your ground speed to be very low. So if for some reason you feel the need to do a power off 180 in a 40 knot wind shear environment, so you’d have to keep it pretty tight to make your spot. I wouldn’t try or recommend this.

[digits_]

If there actually *is* windshear, it would probably be a bad idea. But the problem with windshear reports, is that they are often inaccurate, and even with the current technology on board, often subjective as well.

[youhavecontrol]

40kts? I wouldn't risk it if someone reported that. 20kts... it could have been a random gust while someone wasn't holding their airspeed, but 40kts is quite a lot. That's a big chunk of your airspeed. I'd think a Cessna, or any light plane would fail to keep any altitude or control with a sudden shift of wind by a factor of 40kts.

[rookiepilot]

Is it save to fly(and land) the C172 if there is a wind shear (almost entirely headwind) of 40 kts reported at 500ft AGL? If so, is there anything that I need to look out for when doing a power-off 180 approach?

No.

Their have been a couple of times when I flew when winds were too strong for the environment and my aircraft.

The worst I had was at a mountain airport in Arizona. A 30 knot headwind almost completely disappeared. I was mentally ready, even though no windshear was reported prior --had extra speed on, high approach, and still the aircraft nearly stalled, and found my nose pointed right at the ridge the airport sat on.

Not interested in a repeat experience.

[photofly]

Depends on the vertical range over which the wind varies. There is often 40kts wind shear between he circuit and the ground at YTZ - not unusual to have 30kt headwind in the downwind and 10kts on the nose at touchdown, and it’s a non-event.

Mountain winds might be different, but in the flat, It’s never bothered me. YMMV.

Anyway, windshear means different things to different people, and multiple physical phenomena are all called windshear, so I guess the best answer is “what kind of windshear”?

[rookiepilot]

Depends on the vertical range over which the wind varies. There is often 40kts wind shear between he circuit and the ground at YTZ - not unusual to have 30kt headwind in the downwind and 10kts on the nose at touchdown, and it’s a non-event.

Mountain winds might be different, but in the flat, It’s never bothered me. YMMV.

Anyway, windshear means different things to different people, and multiple physical phenomena are all called windshear, so I guess the best answer is “what kind of windshear”?

I've noticed that at YTZ too (not sure I ever saw 40 knots).

Wind at circuit height is strongly from the west, transitions to landing with a small headwind on 08. Don't recall any issues.

Do you know why that happens there?

[photofly]

Do you know why that happens there?

I don't, but I imagine the lake has something to do with it - smooth terrain, lack of mixing when certain pressure patterns occur. But no, not really.

[rookiepilot]

Found this on the Sedona airport, which is known for its terrain generated turbulence, and talks about wind effects. There have been a number of accidents there.

https://www.boldmethod.com/learn-to-fly ... owndrafts/

When I was there, I had to land on rwy 21 due to the winds, which means kissing the ridge to the north, turning final and dropping fairly significantly to the runway. One of the most interesting landings I can remember.

[youhavecontrol]

Depends on the vertical range over which the wind varies. There is often 40kts wind shear between he circuit and the ground at YTZ - not unusual to have 30kt headwind in the downwind and 10kts on the nose at touchdown, and it’s a non-event...
...so I guess the best answer is “what kind of windshear”?

Agreed... although I'd call it a wind shift more than a shear. There's many times where I've seen the winds on approach still reading 40kts over the FAF, when the ATIS is calling calm winds. I'll brief "possible wind shear" on the approach to the Pilot-not-flying... followed by a gentle almost non-event transition from 40kts to nothing. This is super common in the winter with low-level jets. It's the unexpected mechanical mixing where I find the sudden wind shift/shear becomes more abrupt and messes with the approach profile. At my home airport, one runway has a nasty habit of wind shear, but the other side of the approach is almost nothing ever.

It's also worth noting that the interpretation of "wind shear" from one pilot to the other can vary greatly. I take note when a GA pilot in a Cessna reports wind shear, but I really pay attention if a Dash-8 reports it.

[photofly]

Agreed... although I'd call it a wind shift more than a shear.

That's why you have to ask what the OP was referring to. NavCanada calls it wind shear in the METAR though, and I am happy to follow their lead.

There's many times where I've seen the winds on approach still reading 40kts over the FAF, when the ATIS is calling calm winds. I'll brief "possible wind shear" on the approach to the Pilot-not-flying... followed by a gentle almost non-event transition from 40kts to nothing. This is super common in the winter with low-level jets. It's the unexpected mechanical mixing where I find the sudden wind shift/shear becomes more abrupt and messes with the approach profile. At my home airport, one runway has a nasty habit of wind shear, but the other side of the approach is almost nothing ever.

It's also worth noting that the interpretation of "wind shear" from one pilot to the other can vary greatly. I take note when a GA pilot in a Cessna reports wind shear, but I really pay attention if a Dash-8 reports it.

I figure it's a lot harder to deal with in a Dash-8. A Cessna can nose down and recover airspeed very quickly. Alarming, perhaps for the passenger, if there is one, but not a big deal. I'm not sure how a Q400 would respond, and what the people in the back would say. Any thoughts?

Also, Q400's have a higher rate of descent, so the effect of the vertical gradient is more rapid.

One nice thing about losing headwind on descent is that you make it back up on the climbout - "wheeeeeeee!!!!!". To be honest I find it more awkward to deal with an increasing headwind on descent, which, if you're not anticipating, makes it awful hard to get down to the runway and kills your climbout on the "go".

[fish4life]

Q400 would deal with it better due to the excess power they have, 10 000+hp can get you out of a lot of situations although not something any pilot should go out seeking.

[TurkeyFarmYQX]

Seems like poor pilot decision making.

[CensoredLF]

Is it save to fly(and land) the C172 if there is a wind shear (almost entirely headwind) of 40 kts reported at 500ft AGL?

Yes

If so, is there anything that I need to look out for when doing a power-off 180 approach?

Yes, don't do it. Power off in a wind shear situation is a place you never want to be, doing a 180 power off in strongly variable winds, thanks pdw, sounds like a quick way to die.

I fly in the mountains a lot. The first time I approach a lot of airstrips I do not know whether there is wind shear but it is not uncommon. So...

In a 150, fly your first approach as a go around, 100 ft high and 10-20 knots fast. If you drop you have time to recover and go home. Fly your second approach 50 ft high and a little fast, if you drop you have time to consider whether to land or go around and try again, or go home

Do not force it, be willing to try repeatedly and be willing to fly away.

YMMV
CLF