Ice!!
Ignorance is bliss
I have flown with many pilots over the years on seemingly endless flights, and for conversation’s sake, during the cruise phase of flight, I will ask them if there is anything that has scared them while flying.
There are a few scary stories of near mid-air collisions, engine failures, fires, or severe in-flight icing, but, by far thunderstorms top the list of more near-death confessions by my aviator colleagues than any other aeronautical hazard.
I too have had my fair share of angry cumulonimbus encounters and thanks to my fighter flying days, I’ve changed more than my share of underwear due to near impacts with either the ground or other aircraft and the angels have certainly had their hands full looking out for me and many of those with whom I flew during my F-4 and F-16 days.
While spring and summer are the major growing seasons for thunderstorms, winter is when Jack Frost awakens from his slumber to spread his icy chill and imperil aircraft with a coating of ice crystals; there are times that no matter how hard you try, you cannot escape Jack’s icy clutches.
Since the inception of aircraft ice forming on an aircraft’s external parts has caused many, many fatal crashes. Both the FAA and NASA have done much research in the quest to learn how to mitigate the dangers of airframe icing on all types of aircraft.
Prior to flying in the military and airlines, I avoided clouds like they were the plague particularly when I flew light, general aviation aircraft and most particularly when it was below freezing outside. I was scared to death of getting icing on my airplane and possibly crashing. The book Fate Is the Hunter, has a very harrowing story of Ernest Gann encountering severe icing in a DC-3 over eastern Tennessee. And my father too, in his own adventures had to make an emergency landing, in below minimum weather conditions, in Rochester, New York, one winter after encountering the same conditions as Mr. Gann, and in the same type aircraft.
While I can’t say I ever came close to the adventures of Mr. Gann or my father with regards to icing, I did have one severe icing episode that got my attention and to this day it is the worst in which I’ve ever flown.
On December 15, I departed a southern city in an MD-10 (think DC-10 airframe mated with a MD-11 glass cockpit) bound for MHT (Manchester, New Hampshire). This was the first officer’s original trip but, for me, I had “bumped” another captain (he gets the trip’s pay, I just get my hotel paid for and per diem), the original owner of the pairing, as I wanted to visit my old alma mater and some former college buddies who lived nearby.
Originally, the flight was supposed to go direct to MHT. However, the Northeast had been hammered by its third winter storm, in almost as many weeks, and the dispatcher wanted us to fly to EWR (Newark, New Jersey) first because of some uncertainty about the condition of the taxiways and runways at Manchester.
Upon our arrival in EWR, we were immediately dispatched, as soon as we could unload/load cargo and gas up, to MHT since the field was now open and the weather was improving “rapidly.” I do not recall the exact meteorological conditions but I do recall the ceiling as being around 1,600 feet with two miles in “unknown” precipitation.
In thirty-one years of aviating, I had never heard that one before—unknown precipitation—so I asked the dispatcher if he could call the tower and make that “unknown precip.” known to the FO and me.
The winds at the destination were from the northwest and fairly light but forecast to gain in strength as the day matured and as a high-pressure system pushed away an unwelcomed low.
Finally, with regards to the weather brief from the dispatcher, he said, “Oh, by the way, there is a forecast for a chance of icing in the MHT area.”
“Yeah, I’ll bet,” I mumbled to him as we exchanged happy holidays and goodbyes.
After an hour of the usual ground stuff in EWR we pushed back from the gate. It was exactly 7:38 a.m. After waiting in the morning rush hour traffic, we departed for MHT with me flying this leg.
The actual climb, cruise and initial descent went about as normal as you can get. We were given a very early descent as we approached the airport from the west, from over New York state and southern Vermont.
At 7000 feet, and still quite a way from Manchester airport, we were just skimming above a vast sea of slightly bulbous, and very dense looking clouds. In contrast, above those clouds there was nothing but blue, the richness of which, in hue, caused you to feel you were looking up, into a deep blue sea.
To add even more visual drama while looking out the front of the aircraft, the early morning sun was almost directly in front of us, warming the cockpit, while just ever so slightly below the aircraft those previously mentioned and fantastically bright white clouds rushed by, their numbers forming a impenetrable barrier between our aircraft and the ground, which we knew lay somewhere below.
The harmony of my daydreaming as we serenely cruised just above the clouds was disturbed by the Ding! of the ACARS. A message from the company, from the dispatcher, said that the unknown precipitation was ice pellets, however, the latest ATIS, again, had “unknown” as the impediment to its two-mile visibility, so I guess ice pellets were designated as “unknown” to the automated weather apparatus that did the hourly observation reports.
In preparation for our descent into the clouds, I asked the FO to turn on the engine and wing anti-icing (the windshield heat goes on at 18,000 feet on all arrivals). In fact, every now and then, as we flew level at 7000 feet, we would fly through an occasional pert cloud, one that was poking its head just a bit higher than the rest, and in that brief meteorological foray we would accumulate a bit of ice on the wipers. This “bit” of ice was just a portent of what was to come.
After maintaining 7000 feet for what seemed an eternity, Boston Center cleared us down to 5000 feet and turned us over to Manchester Approach Control. Immediately upon entering the clouds we started picking up ice. I could see it build up on the wiper blades, which are located at the very bottom of the left and right front windscreens. Since we were the first aircraft into MHT that morning, we were the weather ship for all that followed, and indeed a Southwest flight was about thirty miles behind us flying a similar route. I told the FO to report the icing to the controller.
I will tell you that I did not, nor do I, as I type this, consider myself an expert with regards to the intricacies of airframe and/or meteorological icing. As I said earlier, when I flew civilian aircraft, before entering the military, I never ventured into a cloud in anything but the warmest of days or nights. And though I flew F-16s and F-4s in the USAF, throughout the United States and in all kinds of weather and during all four of the seasons, I can’t say I can ever recall, save for one time while leading a flight of four F-4s on a very wintery day, where airframe icing was ever an issue. As far as I was concerned, those fighters were built out of Teflon (the only deicing they had was for the engine intake[s]). Upon being hired by my airline and going through the usual training, for each successive aircraft as I climbed the seniority ladder, I can’t say icing was discussed in any depth at all. My company’s MD-11/10 flight crew manuals do mention cold weather procedures and limitations, as does our company’s flight ops manual, but other than discussions with my dad, about how to deal with wing ice, I can’t say I have ever really talked to other pilots, nor had I been instructed in any detail about it (icing). And in practice, before this flight, I felt the aircraft I flew were ice-proof. In my twenty-seven years with my employer, sixteen of those on the MD-11/10, icing had never been a factor . . . ever. In my opinion, icing was only a concern if you flew small general aviation aircraft.
With that said, I will also tell you, because of my “ignorance” about icing, that, at first blush, I thought it was moderate mixed icing that we were encountering and asked Ben, the FO, to report it as such to the controller.
After being turned over to approach control they informed us that we were going to be vectored for the ILS to Runway 35, which jived with the active runway mentioned on ATIS and also was the approached I briefed with the FO.
The approach controller appreciated the icing report and asked us to report any changes in the weather and also asked for the “spot” winds occasionally. Since we were number one for the ILS, I slowed to 160 knots and dirtied up, slats out, in preparation for a slam-dunk approach onto an abbreviated final.
The actual vector onto final didn’t happen as quickly as I thought it would. We were taken down to 3000 feet, where we droned a bit, and then finally cleared to 2000 feet and turned onto final and cleared for the ILS.
The MD-10 has six rather large cockpit windows, three on each side. The front four of these six windows are electrically heated with heating coils running between the panes of glass and the last windows, number one and six, on the far left and right sides respectively, which are defogged with warm air blowing on them from inside the aircraft. In my entire life, I have never seen a window, even one that was not heated, get any ice accumulation. Well, I gotta’ tell ya . . . today, as we intercepted the localizer, the only windows that we could see out of were the two front windscreens. The other four windows were completely iced over and very opaque; about all they were good for was day/night indicators. Hell, the biggest aircraft in the world could have been about to broadside us, and unless it eclipsed the morning’s sun, not that we had a lot of that at 2000 feet, we would not have been able to tell.
I won’t be proud and say I was not concerned by this rapid and extensive ice accumulation. I was secretly converting carbon to diamonds with my sphincter muscle and laying them on my seat. I told the FO to tell approach, before signing off, that we were in, now, what I thought was heavy icing. (In actuality, the FAA defines in-flight icing as light, moderate, or severe; “heavy” is not a correct icing PIREP[1]. (I kinda knew that, but I was not about to look for the definitions of icing in our company flight manual at that point and search for the proper phraseology.)
What I have not mentioned, until now, is that, since the time when we turned on the wing anti-ice, we had been getting a continuous “level two” (requires immediate crew attention and subsequent action) master caution alert on the EAD (emergency alert display). The aircraft warning system was telling us that the bleed air from both the number one and number three bleed air systems was not putting out enough hot, engine bleed air for sufficient anti-ice of the wings. However, this had been a problem since the MD-10’s introduction to line ops and a new, like BRAND NEW, procedure in the quick reference emergency procedures said that as long as the bleed air temp was above 110 degrees Celsius, it was 180, and the pressure was above 40 psi, it was about 41 to 42, then we were okay (it was not an either/or proposition, they both had to be above the nominal values). I would rather have been Chuck Yeager, zooming through clear air en route to a new supersonic record, than to have been Jack Frost, as I felt I was that day, proving that the Boeing engineers might be right.
Established on the final approach segment with flaps fifty and gear down, yeah, I know, you are thinking the less flaps in icing the better, but I needed the drag of fifty flaps, with the resultant power increase of the engines, to keep the bleed air pressure above 40 psi. Anyway . . . established on final the wipers had picked up a lot of ice, but the front windscreens were still very clear, except for the edges. Tower was reporting the braking action as fair, with patchy ice and snow, with no precip. Since we were so light and slow, approach speed was 135 knots,( Vapp[2]), I wasn’t worried about stopping on a 10,000-foot-long runway with a rather stiff wind blowing right down the runway. I was worried about airframe ice though, deteriorating the aerodynamic qualities of whatever wasn’t de-iced, the tail for example, and the possible extra weight of airframe ice, so I did bump up the airspeed five knots above our normal approach speed. To be honest, I had no idea if that was a valid thing to do, but with the reality of winter encasing my aircraft, at the time it seemed a prudent thing to do.
Instead of breaking out of the clouds at 1,600 feet, down we continued, fully immersed in old man winter’s huff and puff, all the while the FO and I discussing the options if we had to go missed approach. I told him if the bleed pressures ever sustained themselves, for even a few seconds, below 40 psi then I was going to hit the go around button and get out of there.
We finally broke out of nature’s embrace at 500 feet. The visibility was the reported two miles or better and I disconnected the autopilot after clearing the cloud and landed manually. The aircraft felt fine as I flared and stopped.
Clearing the runway was a bit of a challenge since I could not see too well for the turn off, since the side windows were totally obscured with ice, however, after landing they soon began to clear and I did manage to turn off runway 35 and taxi to our ramp.
As I was directed by three mechanics into parking, actually only one working the parking wands while the other two stood nearby, they were all giving me that RCA Victor dog (head tilt) stare as we pulled in to a stop. That got me wondering.
Upon deplaning I walked around the aircraft. I owed the Boeing engineers an apology from my silent cussing of them in flight as the ice accumulated on the windshields because they were right…wherever the aircraft was de-iced there was not a spot of ice, the wing leading edges and wing itself were completely clean, but, where no heat was applied there was about four to six inches of (ice) accumulation, depending on the surface. The tail, which had been a big concern of mine, as I thought it could stall if it picked up a load of ice, was fairly clean but did sport some sizable accumulations in certain places. I was amazed at how relatively ice free the tail was because, unlike the MD-11, it is not de-iced and has no heating applied to it; my concerns about it were, in retrospect, unfounded.
Would I do anything differently if I were to fly into the same weather again? Really, no. Our company’s flight operations manual does forbid us to fly in severe icing; but after looking at the aircraft upon block-in, I can’t say the aerodynamic qualities of the aircraft seemed compromised in the least. I later heard from some colleagues, whom I respect, that the combined weight of the ice upon the aircraft is the real danger when in icing conditions (assuming you have effective wing de-icing capability) Adding five knots for airframe icing, as I was told by another, more experienced captain, is not a bad idea to account for the extra weight of possible airframe ice, if landing distance is not a factor, but, he said in his career that he has never worried about airframe icing on a transport category aircraft on approach, just ice on the runway.
COPYRIGHT NOVEMBER, 2021 Roger Blair Johnson
https://www.amazon.com/Roger-Johnson/e/B087CBSVWF/ref=aufs_dp_fta_dsk