…as in, slipperier than. Before DuPont scientist Roy Plunket accidentally discovered Teflon in 1938, engineers at Fiction Friction, LLC were coaxing owls to excrete the substance, analyzing its molecular structure. What, you’ve never seen an owl sneeze into a beaker? The project was abandoned after a marketing test with homemakers was snot received well. Long before this, archeologists had discovered that O.S. was the secret in moving blocks to build the pyramids. It wasn’t aliens, it was owls.
Mechanics and machinists reference the slippery compound when describing a lubricant that works really well; it’s perfect. Machine parts using a lubricant with a coefficient of friction (Mµ – pronounced: mew) comparable to the owl’s natural and biodegradable emollient would never, ever experience wear. Even though my suggestions to include a reference to the material in the AIM have been ignored, an excellent method to categorize extremely poor braking action is to use the SaOS / Mµ: Slippery-as-Owl Snot / coefficient of friction (© 2016). It’s one notch slipperier than nil-braking and could be used for any reports of less than 0 on the ICAO Mµ scale.
What brings up such a disgusting description and fabricated history? And why the need to debate another reference for indescribable slipperiness? Well, my fellow aviators (which includes 216 species of owls, btw), to wit: for only the second time in 40 years of using aerodynamic and mechanical devices (wheel brakes, spoilers, speed brakes, thrust reversers, a tail hook, drag chute and once a cabin door) in order to stop my flying machine, I couldn’t stop. This time it was a 140,000 pound airliner going down a sloped taxiway – with another airliner in front of me experiencing the same SaOS/Mµ. The first time was in a Cherokee 140 in Plainwell, Michigan (61D) in 1975.
This Fool Escaped
The runway in Plainwell is East/West and 2,650 feet long. Plenty of room for the mighty Cherokee piloted by a modest, but brilliant, teenager. Unless, that is, the runway is SaOS. The field is uncontrolled, no other aircraft were on CTAF, no one manned the FBO radio and it was night. No one was there to provide a field report. I was with a high school buddy and we landed to the East, close to the right spot but a bit long. A couple of seconds after touching down I applied the toe brakes. Nothing. Release and re-apply. Nothing. I quickly unlatched the cabin door and instructed my friend to hold it open against the wind. Using full-up stabilator and the open door, I was able to slow to about twenty knots before we ran out of runway. As the end of the runway neared, with a three foot berm of snow approaching the nose, I remember thinking that I didn’t want the prop to hit the snow bank. Out of intuition, instinct or fear, I shoved the right rudder pedal to the floor. We slid 90 degrees sideways the last 100 feet, coming to rest with the left wing three feet over the berm. Thank you, Piper, for wing dihedral. No problem: taxi to the FBO, drop off my friend, and head back to AZO. It was one of a handful of times that fate was the hunter and this fool escaped.
One final blast of cold, wet weather rolled through the Eastern U.S. recently. Winter’s parting shot wreaked havoc on both surface and air transportation. It also caused the second event in 40 years when I couldn’t stop my airplane due to SaOS surfaces. On the last day of a four-day trip, we were reassigned to work from RDU to DFW then deadhead (ride in the cabin) to ORD. We would take off two hours earlier (at 0550) than originally scheduled and get to ORD four hours later. During the ride to the airport, it started to rain– kind of. As I like to say, the rain hitting the windshield sounded a little “thick.” By the time we exited the van at the RDU terminal, the ground was coated with a quarter-inch of ice and snow pellets. Our plane had been on the ramp overnight and was coated as well. The deicing location is on the opposite side of the field from our gates. Taxiway Charlie in that direction is uphill going east and of course, downhill coming back west. We were one of the first to taxi that morning so little was known of field conditions and none of the taxiways had yet been cleaned. Since we would be nearer 5R after deicing, ground suggested we use that runway. They were working on cleaning 5L (10,000) but 5R (7,500), was already clean. Cleaned by a unique machine with, apparently, a confusing name.
With a two-person crew, you back each other up and catch each other’s mistakes – like things on a checklist, spotting traffic and sharing tasks when things get busy. You also have someone to verify what was heard on the radio. Or not heard. Joe is my FO on this trip and he’s a retired military pilot. Furloughed for over 13 years, he stayed sharp flying King Airs. Both of us came from the USAF fighter community; he flew F-15’s and me F-16’s.
The military is composed of a widely diverse group of professionals in which discrimination and racism has been virtually eliminated. It took a long time but it’s true and it’s a wonderful working environment. And we all participate in diversity training at our carrier. In a job like this, there is neither a time nor a place for racism, sexism, or any other derogatory ‘ism’. Joe thought that he heard ground control tell a ground vehicle that his “bro’s truck” was on the way to 5L. He was shocked. I had to take a second to regain my composure before telling him that the transmission he heard was the “broom” truck was on its way. The ice pellets were too thin to remove with plows, so the method of removal was by using multiple, giant, broom trucks. The rest of the day he was jokingly addressed as the racist old-white-man.
By the time we finished deicing an hour later, 5L was clean. Cleaned by the BROOM trucks. I asked for braking reports and the Mµ was 40 – equivalent to “good”. It would be a simple matter of taxiing downhill to the other side of the field. Or perhaps not so simple.
This is where we, and the airliner ahead of us, encountered SaOS surfaces as we taxied downhill on Charlie. For some reason, the other plane and I were on different frequencies. Ground called to warn us the aircraft in front was sliding. Thinking back, this should have come as no surprise, since we heard that an airport vehicle had slid off some other taxiway. When I heard the jet in front of me was sliding, I tapped the brakes and braking was poor. Moving at about five mph, I tapped them again a couple of seconds later and had nothing. Not even the sound of the brake pucks squeezing the discs or any physical sensation of wheels touching the ground. I reported this to ground and suggested they close the taxiway. I prepared to use the thrust reversers if needed. Luckily, the jet in front of me was about three airplane lengths away and still moving– or sliding that is. Fortunately, the crown on the taxiway is slight so we both remained on the centerline. At the bottom of the hill was 5L, which had been swept by the BROOM trucks. Ground control instructed us to follow the jet ahead, back-taxi on 5L and turn off about 1,000 feet before the end of the runway. The taxiway from where we exited the runway to the approach end of 5L was just as bad as the hill, but taxiing at 2-3 mph made it manageable. As the sky began to glow on the eastern horizon, we rounded the corner onto 5L, shoved the throttles up and accelerated down the swept surface. The entire length was clean, with a ten-inch berm of ice pellets lining both sides.
The first of April is the day we remember what we are the other 364 days.
– Mark Twain
Braking reports are from other airplanes, a good source of information when available. Mµ readings are taken using ground vehicles and their friction-testing devices employ a trailing wheel. Various types of friction-testing equipment can provide different readings, so not all conditions are reported precisely the same. Also, the tests are accomplished using an automobile at speeds well below our normal approach and landing speeds. So, like the owl story, take the Mµ reports with a grain of salt. Owl snot was never researched by DuPont or Fiction Friction, of course, nor was it found in the pyramids–April fools. But that shouldn’t stop us from promoting the SaOS/Mµ scale in aviation. It can get slippery out there flying airplanes, and not just on the ground. Watch your step, my friends, and have a tissue ready if you spot an owl. •T&T–