Hermine's Revenge

In my 18 years as a commercial pilot, there have only been a handful of approaches memorable enough that I remember them in detail…Dallas, Ft. Worth in an ATR-72 in 1996 when I encountered wind sheer while flying an approach I probably shouldn’t have accepted in the first place…Toronto, Canada in the winter of 2002 in an MD-82, flying an ILS in white-out conditions with a strong 90 degree crosswind to a runway that was in serious need of a plow…New Orleans, as I mentioned in my last post, when I practically lost count of the number of approaches we shot in a single 24 hour period and yesterday, September 8th , 2010 at DFW, flying through the remnants of Tropical Storm Hermine. (The picture above shows the sun coming up over Hermine as she sat on Dallas, Ft. Worth.)

The Today show began this morning with a story entitled “Hermine’s Revenge,” an appropriate title given the events in and around the Dallas, Ft. Worth area yesterday. The airport officially soaked up 5.23 inches of rain as of 3pm, but nearby areas of town recorded as much as 9 inches. There were 5 confirmed tornadoes that touched the ground within the city limits and countless funnel clouds and rotations that mercifully remained aloft. The local stations today are streaming video of homes and businesses without roofs and area residents who were plucked from rising flood waters by fire and rescue crews. Clearly, it was a difficult day for those on the ground, but it was a significant challenge for those of us in the air.

My day started with a 4:15 wake-up call and a 6am departure for a short flight to DFW and a scheduled landing around 8:45 am. I watched the Weather Channel as I dressed at the hotel and couldn’t help but wonder if I would in fact be spending the night at home tonight as planned. We departed a few minutes ahead of schedule with a light load of passengers and enjoyed beautiful clear skies, a smooth ride and a gorgeous sunrise until we got to within about a hundred miles from DFW.

We had ample fuel on board, fully expecting to burn more than planned on this flight. Our official alternates were Dallas Love Field and Tulsa, Oklahoma. I wasn’t crazy about either of these choices...Love field is generally only put on the flight plan to fulfill a legal requirement…if you could land at Love, then you could certainly land at DFW, so what good is it? Tulsa would normally be fine, except that yesterday, there was a line of storms between DFW and Tulsa that I didn’t want to cross. The Captain and I discussed this before we departed and preemptively decided that something west of the airport like Abilene would better suit our needs. Hopefully we wouldn’t need it.

About a hundred miles out of DFW and just about the top of descent, we were told to slow as much as practical and told to expect holding over the Glen Rose VOR, a navigation point on the arrival southwest of the airport. At that point we started our calculations for “bingo” fuel. I’ve discussed this before, but bingo fuel is the fuel needed to fly from the holding point to the airport, execute a missed approach then continue from there to the alternate airport and land with acceptable reserves. We calculated our bingo fuel and estimated that we had enough fuel to hold for approximately 30 minutes. (The picture below was taken just prior to entering the hold.)




Holding was short and sweet. We began our entry turn into holding and were then cleared to DFW via radar vectors. The weather at the field was as bad as I’ve seen it in a very long time with heavy rain reported at and around the airport, visibility less than a mile and winds from 140 degrees at 12 gusting to 28 knots. We initially received vectors for the ILS approach to runway 13R, a runway on the far west side of the airport, but as we were approaching the airport, four jets in a row missed the approach due to windshear on short final. With the reports of windshear isolated to the west side of the airport, we received clearance to land on runway 17C, a north-south runway on the east side of the airport.

The ride during the last ten to fifteen minutes of our arrival was pretty uncomfortable. We entered heavy rain about 30 miles from the airport and endured continuous moderate turbulence and airspeed fluctuations as high as 25 knots until about 1500 feet on the approach. The speed fluctuations calmed down after we joined the final, which was a good thing, since anything more than about 15 knots inside the final approach fix would probably result in a divert.

As an added concern, the rain was so intense that our on board radar was attenuating. Radar attenuation occurs when a strong weather cell reflects all of a radar signal, preventing that radar from detecting any additional cells that might lie behind the first cell. When approaching a line of thunderstorms and trying to find a path through to the other side, it is good practice to tilt the radar down in an attempt to “paint” the ground on the back side of the storm. If you are unable to paint the ground on the other side of the storm, then the weather ahead is so dense that the radar signal is unable to penetrate it and thus, unable to detect what may be on the other side. For us, the intensity of the rain was preventing the radar from being able to “see” more than 5 to 8 miles ahead of the aircraft. In this scenario, a pilot is forced to rely on reports from aircraft ahead, ground radar and what little warning is available from the limited sight capability of the on board radar.

Regional Approach Control brought us in 10 miles in trail of the aircraft ahead and vectored us to intercept the ILS to runway 17C. Once on the localizer, we intercepted the glide path and began to configure for landing. Thankfully, the turbulence seemed to subside somewhat as we descended below 1000 feet and the airspeed fluctuations dropped from plus and minus 25 knots to a little less than 15. The tower was reporting RVR of 4000 feet at the touchdown point, the minimum allowable visibility for me, the First Officer, to fly the approach and land, so I continued at the controls. We were still flying though heavy rain at this point, so I asked the Captain to set my windshield wiper to high as we passed through 500 feet. The Captain activated both wipers and noted that he could see the ground when looking straight down, a good sign that we would soon see the runway. At about 400 feet, the approach lights came into view and the runway was in sight shortly thereafter.

There is such a thing as touching down too smoothly. It is possible to waste thousands of feet of runway while holding the jet off in an attempt to “grease” it onto the runway. (The touchdown is the only thing anyone remembers.) When landing on a wet or short runway, it is much better to comfortably, but firmly place the aircraft on the ground. If you’ve ever sat near the wing on a large jet, then you have seen the ground spoilers deploy after touchdown. These spoilers, depending on the aircraft, are usually activated by a “weight on wheels” switch or by wheel spin-up. If an aircraft lands too smoothly, especially on a wet runway, then the wheels will not spin-up and there may not be enough weight on the wheels to deploy the spoilers. The spoilers are designed to do two things, both important when landing in inclement weather or on short runways. First, they create drag. Second, they kill lift and put the aircraft’s weight on the wheels allowing more traction and more effective breaking. Both are vitally important.

In this case, we touched down smoothly enough that the spoilers did not deploy. I felt two expansion joints in the runway pass beneath the main gear with no reaction from the spoiler lever, so as I lowered the nose to the runway, the Captain manually deployed the spoilers, which put our weight where we needed it and gave us the traction we need to stop the aircraft on the runway. The runways at DFW are both grooved and shaped in such a way that water drains to the side. So as I applied the brakes, the aircraft felt more like it was on a damp runway than on a runway subjected to hours of heavy rain. We slowed at a normal pace and exited the runway.

I must admit, that I can recall precious few approaches that successfully elevated my heart rate. I pride myself in being good at what I do and being calm and professional as I execute my duties. This approach…got my heart beating. As we cleared the runway I became aware that my heart was racing and that I was very happy to be on the ground. There’s an old aviation saying…maybe you’ve heard it…that it’s “better to be on the ground wishing you were in the air than in the air wishing you were on the ground.” I was very happy to be on the ground.