Airliners in Weather: What the Hail?


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Recently, a Boeing 787 and an Airbus 320 made headlines with dramatic photos of hail damage to the radomes and leading edges of the airfoils. That type of news story prompts the question from friends, family and passengers, “Can’t pilots see hail coming?”

My answer is threefold: yes, no, and it’s not that simple. Let’s take each part in order.

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On a normal flight, the above outside view would be depicted like this on a cockpit nav display:

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The magenta line is our filed flight path–where Air Traffic Control (ATC) expects us to be. To simplify for the sake of brevity, green areas are precipitation, red, convection, meaning uplifting air.

So yes, we can often see it coming because we know that convection can heave massive amounts of moisture upward with great force, into altitudes where the temperature could easily be -35C or less. This flash-freezes the moisture into ice pellets, with the size determined by variables of speed and temperature. I’ve felt and heard the sizzling sound of such particles impinging on my aircraft at over 40,000 feet–they’re fairly tiny and mostly innocuous at high altitude–not so in the lower, denser air.

Regardless, here’s where the “no” of my tripartite answer comes in. Like the ill-advised New Year’s Eve tradition some gun owners have of celebratory fire, what goes straight up comes back down–but the question is, where?

An enormous volume of hail spewed from the top of a thunderhead will get caught up in the winds aloft and they vary from near zero to over 100 mph. It’s not unusual for wind to blow a hail storm ten or more miles from the core of the thunderhead that lifted the moisture in the first place.

At night, the lightning may be obvious, but storm contours are not.

At night, the lightning may be obvious, but storm contours are not.

Can an you see that on radar? Maybe. Normally, you have the radar looking ahead, not up. What was a clear path, suddenly may be filled with hail, even miles away from the original source.

Which brings me to “it’s not that simple.” Both of the recent hail damage incidents occurred at low altitude, and by that I mean below 20,000 feet, which is a complicated area: jetliners don’t cruise that low, so the airspace is filled with a conflicting mix of climbing and descending aircraft. ATC does a fantastic job of sorting the mix crammed into often constrained airspace. But the problem is, that doesn’t leave much room for deviating around weather.

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In fact, with so many aircraft being managed on a particular frequency, it’s extremely difficult to even get a course change request to ATC. Add to that a ground speed often between 200 and 300 miles per hour and you have a dilemma: yes, you can see some weather threats, no, you can’t see all of them and avoiding weather and other jets in crowded airspace is simply put, not easy. Things change rapidly, virtually by the minute, and we’ll cover many miles in that time.

I can’t stress enough how versatile and responsive ATC is in managing tight airspace filled with dissimilar aircraft on assorted routes and changing altitudes. But as the mix becomes more dense, this high-speed Rubik’s becomes an outlandishly devilish puzzle.

In the cockpit, know that we’re using every means at our disposal to detect and track weather. We gauge the wind effect out of the top of a storm, we plot a course upwind of effects, we pass along what we’ve found to ATC and other aircraft.  Count on the reality that everyone on the ground and in the air is doing everything possible to avoid or, in the worst case, escape from bad weather.

Even the fact that only two aircraft out of the thousands in flight that day made the news with hail damage is good news in itself: pilots and ATC are pretty good at handling weather. Still, there’s only so much room and little leeway to detect and avoid hail.

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That’s the real news, and the good news far outweighs the bad: flying to Philly yesterday, I can’t compliment both ATC and the dozens of other pilots in the air for sharing information about clear passages, turbulence and new routings. I don’t know how Center and Approach do it, but the responsiveness and quick reaction is amazing.

I’m especially grateful that my airline has made installation of cutting edge radar technology in my cockpit a priority: yes, it’s expensive, but they want me to have the best, most current weather picture as I approach a front with you on board.

Our newest radar–which I’m glad to have available–displays three dimensions, is linked to our nav system so it always knows exactly where it is and thus screens out ground clutter and geographic features, and displays a predictive movement of hazards. It’s always on, scanning for potential problems and will pop up on cockpit displays if it detects something even if we’ve selected another depiction.

So there you have it. Yes, no, and it’s complicated–those are my answers to the question, “Can’t you see hail from the cockpit?” The big-picture view is that we’re all working together to stay out of the headlines. I’ll be flying to LaGuardia and back tomorrow and the fact that you WON’T read about my flight underscores everything I’ve just said.

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7 Responses to “Airliners in Weather: What the Hail?”

  1. Randy Sohn Says:

    Yup Chris, ” ’tis a problem, ’tis”. Always has been and always will be, I guess! You didn’t mention that 747 that also got the dickens beat out of it over China. I’ve had the Korean air traffic controllers become exceedingly nervous when I deviated a few miles north of track between Japan and Seoul, they’re extremely aware of the 38th parallel’s proximity! I assume that also played a big part in that most recent Chinese event, I dunno. In the early days of airborne radar I strongly was (and remain) a big fan of the “C” band for radar but events conspired and now “X” band is the only thing available. “C” attenuates less than “X” does, thereby letting you see through the storm immediately in front of you and probe for the possibility of another one behind it. Anyhow, as you said, we all wish that we could see it all so simply!

  2. Chris, there should be a regular column of your explanations for the not-knowers somewhere..,
    Well said, and your boss is happy as well, I think!
    Martin

  3. peggywillenberg Says:

    Thanks for this explanation! One question, when you say “…and displays a predictive movement of hazards”, are you describing so-called “future-scan” simulation, based on current conditions and a predictive algorithm? If that is the case, that is a pretty impressive piece of software to have in your cockpit. Although this product is available at some of the larger local TV stations, I had no idea it had been applied to airline use yet. Kudos to AA for spending the $$$ to equip their planes this way.

  4. Great info as always Chris. One question though- since you mentioned LaGuardia , now that they announced a major renovation of the airport- do they ever ask the Pilots what they could do to make the new airport less like the “old LaGuardia” ?
    Or do you gets what you gets?

    • Ain’t nobody asking the pilots. They’ll spend $2.4 billion on a new terminal, but outside it’ll be the same marginally useful 7,000 foot runways with no overruns, three out of four of which will land you in the drink. But they’ll have Chipotle and pet urinals in the new, cosmic terminal.

  5. Greg Poulsen Says:

    Hi Chris,

    I had a coworker on the Delta flight that deviated to Denver (I was on the earlier Delta BOS-SLC flight). He said that it was “interesting” for about 2 minutes, when the turbulence was pretty exciting and the sound of hail hitting the fuselage was quite loud. I did want to point out one item. At the time of the incident, the plane was at cruise altitude, as it was not yet close to Salt Lake. His recollection was that they were at FL 350, and I think I saw the same thing in new reports.

    Thanks for the insights from the cockpit perspective. As a 100K mile / year passenger, I am grateful for professionals like you who make my life so much safer and (usually) more comfortable and predictable.

    Best,

    Greg

  6. Great write up. Has been some crazy stories lately of planes and hale damage. I am certainly grateful I’ve never experienced it.

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