In the wake of several recent airliner losses, talk in the media once again turns to the futuristic concept of remotely piloted passenger jets.
A very bad idea, as I explain on Mashable.com. Just click here to read, or use the link below.
Network news media love a screaming headline, even if they have to fudge the facts to suit the rhetoric. But here is the reality behind the wailing and gnashing of teeth regarding recent ice-related delays at major airports: the airlines did a damn good job given the challenges heaped on them in this storm.
As a captain, I flew a 737 trip in the middle of the week in the slush and snow out of DFW. Here is your chance to bypass the media frenzy (NBC News carefully crafted “9 hour delay for passengers”–quietly admitting later that it wasn’t on-board) and watch the flight evolve despite the weather interference.
At 06:10, a phone call from crew schedule woke me up. I had volunteered to fly a trip that day and they offered one, a turn to John Wayne Orange County (SNA) scheduled to depart at 10:10. I agreed to fly the trip.
Normally, it takes me 35 minutes to drive to DFW. I left my house at 6:45 to allow extra time for the slush and snow snarling the highways.
I arrived at DFW an hour later, an hour and twenty minutes early. The jet was parked at the gate, had been all night in the freezing precip, so I went aboard and started powering up systems. A quick check of the wings and fuselage confirmed what I assumed driving in: we’ll need a good de-icing on the wings, control surfaces and fuselage.
Let’s get more specific about aircraft icing. First, we need to remove the accumulated ice. Second, we need to prevent more ice from re-forming on aircraft surfaces. De-icing can be accomplished by a number of different fluids under pressure. “Anti-icing” is provided by a different, specifically designed fluid that chemically inhibits the adherence of ice on aircraft surfaces.
In our case, the ceiling was low and visibility limited by ice fog, confirming the critical temperature-dew point spread that leads to condensation which of course would freeze on any cold surface. That means both de-ice and anti-ice will be required.
Anti-ice fluid effectiveness varies with temperature, and rate and type of precipitation. The duration of anti-ice protection declines as various forms of moisture increase. So, gauging the time–called “holdover time”–is a call that must be made by the flight crew based on observation of conditions actually occurring.
You can tell when anti-ice fluid has been applied to a jet because it will be colored either brick red-ish or lime green. The intensity of the color cues the cockpit crew as to the fluids declining effectiveness–it fades as the fluid loses the ability to inhibit icing. We actually check visually that from inside the aircraft prior to takeoff.
A side note about the fluid color. Most airlines now use the green fluid because the red was difficult to distinguish from hydraulic fluid as it dripped from crevices and bays on the aircraft, sometimes several flights downline from the original de-icing treatment. I learned long ago how to differentiate the two: propylene glycol, the main ingredient in anti-icing fluid, smells and tastes sweet. Skydrol hydraulic fluid is bitter. Yes, I’ve tasted both in the thirty years (and counting) I’ve been flying jets and laugh if you want, but it saves all aboard a needless and probably lengthy maintenance delay.
Another unseen complication that adds to the icing mix is jet fuel. The worst case is with fuel remaining in wing tanks after a flight at high altitude. The fuel in the tanks become super cold due to the temperature at altitude (often -50C or less) and as a result, the wing surfaces both upper and lower are super-chilled, causing any moisture in the air to freeze on contact. Explain that to the guy sitting next to you griping as we de-ice on a sunny, clear day: humidity plus ice-cold metal surfaces can add up to wing icing that must be removed: we can tolerate no more than 1/8″ of mere frost on the underside of the wing only. Any other airfoil contamination must be removed before flight.
Clear ice on wings is not easy to see from the cabin, particularly the area near the wing root, which is critical on aircraft with tail mounted engines like the MD-80 and -717, because upon wing flex as rotation and liftoff occur, any wing root ice that breaks loose into the slipstream could easily fly back along the fuselage to be ingested by either or both engines, with potentially disastrous results.
So why don’t aircraft have heated wing surfaces? Actually, most MD-80 upper wing surfaces do have an electrically heated thermal blanket on top of the inboard-most portion of the wing surface. But, not the curved wing root joint which is not visible from the cabin. So, you’ll notice a lot of MD-80 aircraft having to de-ice in even the slightest icing conditions.
In our case, I knew the fuel pumped aboard for our flight would have the opposite effect. At DFW, the fuel is stored underground and pumped aboard from a hydrant, not a truck. The effect would be to warm, not freeze the wing surfaces. That would help with de-icing, but we’d still require a thorough dose of Type-2 de-icing fluid to clean ice off the jet.
By 9:10, the official crew check-in time, there was no sign of a first officer. I started the process of printing a flight release and agreeing on a fuel burn, as well as the complex process of determining takeoff speeds, made more complicated due to the presence of slush and snow on the runway. Any type of contamination, from pooled water to slush to ice can impede both acceleration and deceleration. Both maximums (takeoff and stopping) must be accurately calculated and while there is a published “runway condition,” the actual calculations are very much a realtime, eyeballs-verified assessment: I’ve broken through an undercast during an ice storm as we approached DFW only to find that just the first two-thirds of the runway had been cleared–a fact not noted on the official field report. That lopped off about four thousand feet of useable braking surface.
At 9:30, forty minutes prior to pushback, still no sign of a first officer. The roads are awful, as is the traffic, so I’m not surprised and I’m glad I left home as early as I did. I called Crew Tracking, catching them by surprise as well: in this winter storm, there were plenty of stuck, stranded or missing crewmembers. They hadn’t noticed.
I resigned myself to going out into the sleet to do the exterior inspection myself, planning to have all preflight duties complete in case the first officer should show up at the last minute. Here’s an up close look at the leading edge icing:
and the ice on the wing trailing edge:
Engine covers were installed, a very smart preventative measure to prevent icing, but which would require maintenance removal and documentation. I radioed maintenance to get in the cue for this required maintenance and fortunately, American Airlines had well-staffed maintenance for this shift. But again, they too had technicians who, like my F/O, were stuck in the ice storm snarled traffic, slowing things down.
With the exterior preflight complete, I requested the upload of navigation and performance data as well as our clearances. And I took a minute to call the Crew Scheduling Manager on Duty to suggest that they grab the deadheading 737 first officer sitting in row 20 and reassign him to fly the trip. He said if the duty legality limits worked, that’s what he’d do.
By 10:00, the conscripted first officer was in the right seat, having agreed to the reassignment: he’d fly the leg to the west coast, his home base, and rather than going home, he’d also fly the leg back to DFW and only then deadhead home, if possible. Just one more crewmember going the extra mile to make the flight operation work.
We pushed back nearly on time (10:21 vs. 10:10) , but the ramp was congested with ice and slush, slowing everyone down even further. The precip had stopped, the ceiling had lifted to a thousand feet and the temperature-dew point spread had widened, all of which meant less chance of ice formation. Our holdover time would expand, allowing us to de-ice on the ramp rather than at the end of the runway. Essentially, that made for a shorter wait for all aircraft: if there is freezing precip, or any precip in freezing temps, all de-icing would have to be done at the end of the runway, meaning long takeoff delays.
Taxiing a seventy-five ton tricycle on ice and slush is tricky, requiring slower speeds and a critical energy management: too slow and you’ll have to add excessive power to restart movement, slinging ice and slush at other aircraft. But you also need almost zero forward inertia to maintain nose gear traction in any turn, aided by asymmetric braking on the main gear into the turn. It’s a dicey operation that takes extra time.
We kept the flaps retracted on taxi-out so as to not accumulate any slush or freezing water on the underside of the flaps, a potential problem during flap retraction. Our miles-long taxi from the east side terminal to the west side runway gave us plenty of time to assess the surface conditions and fine-tune our power and speed plans.
We finally lifted off nearly fifty minutes after taxi-out. Through route shortcuts and favorable winds, we made up some of the lost time, arriving twenty-eight minutes behind schedule.
I believe my flight was more typical of all flights during an unrelenting ice storm, but mine isn’t the one craftily worded into a horror story by the media. Regardless, the fact is that icing makes flight operations complex, difficult and challenging. Yet more flight operated in the same way mine did–slow, careful, successful–than the media version of a few unfortunate cases. I take it as a compliment that the reality of these winter flights was a success story leaving the media very few flights to turn into their typically overblown horror stories.
By the time I got home nearly fourteen hours after voluntarily accepting the challenging flight assignment, the network news was already sensationalizing the “impossible” travel situation created by SnoMIGOD 2015 which dumped an unprecedented amount of snow and ice on DFW and Dallas Love Field. At least I knew the facts were not as they’d have us believe–and now you do too.
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Head pounding. Look down at your right calf: a liter bottle of water, mostly full.
Just flew 3 hours from DFW to DCA–should have paid attention to hydration. Now, sitting near the end of runway 1 at Reagan national, it’s too late: the damage is done.
Been sitting here for over two hours now. In a thunderstorm. Which has hit the tower with a lightning bolt that fried their primary radios–so now they’re using a weak backup radio that sounds like the controller is using a tin can on a wire.
More delay while the radio situation gets fixed, plus the hand-offs from tower to departure ain’t working. Wait.
“American 445, go.” Sounds like her head is in a bucket.
“We’re wondering about a take-off time, as we’re bumping up against some Passenger Bill of Rights time constraints.”
Like three hours–an hour from now–then we need to go back to the gate and probably, cancel the flight. Passengers have a right to not go anywhere, rather than sit on a plane waiting to go somewhere.
“We don’t have any information,” comes the tinny reply. Thanks for your help.
Ignored several phone calls from the cabin crew already, saying passengers are antsy, wondering what the latest is. When I ignore the interphone chime, the F/O has to field the questions to which there are no answers anyway. I prefer to isolate myself to focus on weather, fuel, timing, the departure procedure to the north (the FAA will violate you for even a tiny stray from the radial) and a clear path on radar. Which I can’t see because our nose–and our radar dish–is facing south. I make a PA every thirty minutes or so, telling passengers what I know: westbound departures are on hold due to weather on the departure routing. The lady in the tower sounds like her head is in a bucket. I don’t tell them that, but still.
Already tried to negotiate a departure to the south or even east in order to air file a route west–craftily uploaded an extra 3,000 pounds of fuel before pushback, after seeing the storm front marching on Washington as we landed.
More calls from the back: passengers want to use their cell phones; they’re getting up . . .
Tell them no–if they use phones, the cabin crew has to make another aisle pass to ensure they’re off for take-off (FAA regulation) and if we’re cleared, we need to take the runway, check the weather–then go.
Sure, they have connections and people waiting. But that can wait till we get there. What I want to attend to is a new and higher power setting that creates less time on the runway; an optimum flap setting that gives a better climb gradient, and a wind correction to stay on the safe side of the departure radial.
That’s where the “firewall” comes in: if I let connections, cell phones, Passenger Bill of Rights or even my own next flight tomorrow (not going to be legal if we keep delaying) mix with the important considerations like fuel, weather, radar, performance and power settings, something’s getting messed up.
It’s not that I don’t care–I really do. But if I don’t attend to the latter set of considerations, the former won’t matter, will they? Drink some water, rehydrate. Relax. Run through your list of priorities for right now. Pay attention to right here, right now. Be ready to do “now” right; worry about later, well, later. That’s the thunderstorm zen, the captain’s firewall.
It happens fast: “445, start ’em up–you’re next to go.”
Fine. I reconfirm with the F/O the heading plan (310 is good–but 305 is better. If we have to correct back right to the radial, fine–but we do not stray east . . . a full radar picture before we roll, static.”
Raining cats and dogs, hard to see, swing out onto the runway and grab every inch. Stand on the brakes, full radar sweep–decide.
“You good?” I ask the F/O as a formality–because I’m looking at him and I can tell from his face whether he is or isn’t from his look no matter what he says. And if he isn’t okay or doesn’t look okay, if maybe his firewall or zen are under seige, I’ll know and we won’t go until everything adds up.
We roll; relief when we’re past abort speed; mental chant “engines only, engines only” reminding myself of which of the hundreds of warnings I’ll abort for on that rain-slicked postage stamp of a runway; throttles speedbrakes THEN reverse, amen. The jet rockets into the whipping rain undaunted; love the big fans at a high power setting. We climb, buck, dodge, weave and finally . . . cruise at 40,000 feet above all the turmoil as the lights of the nation wink out.
Landing after midnight, home finally at 1:30am. Crew Schedule calls: “Sleep fast, we’ve slipped the departure of your Seattle turn just long enough to keep you legal. You’re still on it.”
Eight hours in the cockpit today; another eight tomorrow. Plus a few hours to sleep in between.
Erase today–it’s over, safely and smartly done. Rest, and save a little zen for tomorrow. No doubt, you’re going to need it.
Take-off? That’s easy, right? You fasten your safety belt, move your seat fully upright and stow your tray table. Ready. Right?
But if that’s the full extent you prefer to be aware of, fine. Otherwise, read on as we take apart this very complex, important maneuver.
The planning starts long before you strap yourself into your seat in the back of the plane, and here’s why.
Take-offs come in all sizes and shapes because of several variables–so there’s no “one size fits all” logic or protocol. What are the variables? Well, aircraft weight, runway length, winds, runway surface condition and temperature are the basics, and each has an effect on performance.
You might think runway length is the great reliever, right? Miles of runway, like at DFW or Denver mean simple, low-risk performance, right?
And you might think a short runway or nasty weather are the “problem children” of take-off performance. But let me give you the pilot answers: no, no, and furthermore, no.
Throw out what you’ve been thinking about take-offs as a passenger, and strap in tight (is that tray table up? is Alec Baldwin playing “Words” in the lav while we all wait for His Highness to finish?) because you’re about to test drive some “pilot think:”
I don’t worry about taking off–I worry about stopping.
Why? This sounds so simple that when you think about it, you’ll have to agree: aircraft are made to fly–not drag race.
Look, accelerating 85 tons to nearly 200 miles per hour builds tremendous kinetic energy. Not a problem for the landing gear if you take off because it’s simply rolling. But if you must stop, the brakes and wing-located speed brakes have to dissipate that energy within the length of the asphalt ahead. The runway length is finite, the aircraft weight is unchangeable once you’re rolling. So where is the point of no return, the point after which there’s not enough runway to stop?
As a pilot–particularly as the captain who makes every go-no go decision no matter which pilot is actually flying–you must know when that instant occurs. That magic point is not a distance down the runway but rather, a maximum speed: “Refusal Speed.” In other words, the maximum speed to which we can accelerate and still stop within the confines of the runway if we choose to abort the take-off.
But there’s a catch, of course.
Refusal Speed is only half of the go-no go decision. Part Two is just as critical: what is the minimum speed I must have in order to take-off if one engine fails, continuing on the other. I can hear this already: why the hell would you want to continue the take-off on one engine?
To which I’d answer back, what if the failure happens above Refusal Speed? In other words, there’s not enough runway ahead to stop your high-speed tricycle.
Okay, that minimum speed–the speed you must have in order to continue the take-off in the remaining runway on one engine–is called “Critical Engine Failure Speed.”
Now you have the two controllers of the go-no go decision; one a minimum speed (you must have Critical Engine failure Speed achieved to continue safely into the air) and one a maximum (if you attempt to abort in excess of Refusal Speed–you ain’t stopping on the runway).
So which is the deciding factor? Well, in modern day jets under average circumstances, the “max” speed is normally way in excess of the “min” speed. In other words, you normally achieve the min required for single-engine continued take-off before you reach the max allowed for stopping. So, in ordinary circumstances, Decision Speed–which we call V1–is Refusal Speed.
In other words, we know we’ll secure adequate flying speed for a single-engine take-off before we hit the max abort speed. So we use the max abort speed–Refusal Speed–for V1.
Pilot-think lesson one: it’s easier to deal with a single-engine aircraft in the air than it is to stop a freight train on the runway. Which goes back to my earlier point: airliners fly great but make only adequate drag racers, stopping on the drag strip remaining being the challenge.
Add to that the wild card: the captain must decide in a split second as you’re rolling toward V1 if any malfunction that occurs will affect the ability to stop the jet: did an electrical system failure kill the anti-skid system required for max braking? Did a hydraulic failure eliminate the wing spoilers figured into the stopping distance?
Some jets require very little system support to fly–but a lot of factors to stop: the MD80 will fly all day without hydraulics, electrics or pneumatics–but it ain’t stopping on a “balanced field” without electrics and hydraulics.
And remember, those speeds are “perfect world” scenarios. But on your flight–like every flight–despite the engineering numbers from which the stopping distance is computed, there are the real life factors which screw them up: wet or icy runway, tailwind, old tires, old brakes, rubber on the runway because of aircraft touchdown on landings.
Now, have you deduced the worst-case scenario with the two controlling speeds, Critical Engine failure Speed and Refusal Speed? That is, you will exceed the max speed for stopping before you attain the minimum speed for single-engine flight?
That’s simple: you can’t take-off. In practice, we adjust the flap setting or even reduce the gross weight: back to the gate–some cargo and/or passengers must come off. Hardly ever happens that we return to the gate because we plan ahead–and that’s why you hear of a flight being “weight restricted,” meaning some seats will be empty by requirement before you even board. Now you know why.
But really, that’s not even the worst case scenario from a pilot’s perspective (sorry about your trip, if you’re one of the passengers left behind on a weight restricted flight–but you probably got some compensation for it). Rather, it’s when the two numbers are the same.
That is, the minimum speed required for flight is equal to the max speed for stopping.
That’s called a “Balanced Field:” the runway distance required to accelerate to minimum single-engine take-off speed is also the maximum velocity from which you can safely abort and stop on the runway.
That’s a “short runway” problem, like in LaGuardia, Burbank, Washington National or Orange County, right?
Wrong–it’s everywhere, like Denver’s 14,000 feet of runway (compared to LaGuardia’s 7,000) on a hot summer day; ditto DFW; also Mexico City even on a cool day because it’s at 7,500 feet elevation. And it can occur anywhere due to rain, ice or snow.
So here’s your plan, and as pilot-in-command, you’d better have this tattooed into your brain on every take-off: once you enter the high-speed abort regime (by definition, above 90 knots), know what you will abort for–or continue the take-off. Be ready for both–without hesitation.
It’s easier to decide what you will abort for than won’t–because the “must stops” outnumber the “can stops” and remember your pilot think: it’s often safer to continue than stop. And here are my Big Four Must Stops: engine fire, engine failure, windshear or structural failure.
So rolling past 90, I’m thinking over and over, “engines, engines, engines,” zeroing in on any malfunction in order to assess if it’s an engine problem–if not, it’s likely not a “must stop” situation; I’m aware of windshear but don’t even start the take-off roll with any of the conditions present; structural damage we’ll deal with as necessary. Otherwise, we’re flying, folks.
Got all that? Good deal: now you understand the important interrelationship between Critical Engine Failure Speed, Refusal Speed and the all important concept of V1.
And now that you understand the complex, split-second conditions surrounding the go-no go decision on your next take-off, you can relax and just put all of those crucial factors out of your mind.
Because rest assured, they’re at the forefront of mine, or that of whatever crew into whose hands you’ve entrusted your life.
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