Saturday, July 30, 2011

Too Darn Hot

Fire in flight! is one of the scariest things in aviation. An engine fire in a single-engine airplane turns you into a glider, since putting the fire out means shutting off the fuel. But an engine fire in a multi-engine airplane turns you into a brick. One of the axioms of multi-engine flying is that in case of wing fire you must put the airplane on the ground now, no matter where you are. There are tales of multis dropping like a rock on downwind.

I was taught that the reason for this was that the aluminum spar got "soft" when heated. This seemed plausible, so I believed it and passed it on. But that's superstition, which has not place in flight instruction.

So here is a graph from Dennis R. Jenkins's X_15: Extending the Frontiers of Flight, a NASA publication available free here.

The graph shows the strength response to temperature for several materials used in aviation: aluminum, magnesium, titanium, stainless steel, and Inconel X. Inconel X can handle amazing amounts of heat, which is why it was used in the X-15. (The Wikipedia article on Inconel seems pretty good.)
The vertical scale is Tensile Yield Stress, that is, how much stress does it take to make the material yield, "strength" in layman's terms. The horizontal scale is temperature.

The aluminum curve is pretty scary: at low temperatures the strength remains about constant, but at about 200F it starts to decline rapidly, and is halved by about 400F.

That's not very hot. As a cook, I regularly touch stuff nearly that hot (I often stir stuff with my hand rather than a spatula). French fries cook at 375F. Typical ITT temperature for a PT-6 engine is about 1350F, and piston EGTs are in the same ballpark.

Aluminum loses its strength at temperatures that are common in aviation!

So, if you are in an aluminum-sparred airplane and there is heat on the wing land right now. Don't try to reach the airport. Land right now on something that won't hurt anybody else.

A composite airplane like the Diamond DA-42, which I believe has a composite spar, might be different. If this is correct (don't take my advice unless you verify that the spar is composite) then the spar should be able to maintain its strength at much higher temperatures, and you have more options as to landing.

[revised 15 Aug 2011]

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Friday, July 22, 2011


[My hotel had connectivity issues, not my laptop. Phew!]

[This is a crude version; I'll clean it up and add pictures after I fix my laptop's connectivity issue.]

Sometime a couple of weeks ago I got a tweet announcing the STS135 Tweetup. STS135 was the NASA designator for the final mission, and a tweetup is a social networking phenomenon where people who know each other online through twitter gather for an event. I registered on the website. NASA took 150 of the rumored 5000 applicants to the launch.

Not me.

NASA opened a few slots for the landing, and this time I got picked! I hesitated a little: it would be expensive, tiring, and tough on my family to have me away again so soon. But I had to go!

So Tuesday I drove down to Salt Lake and flew to Florida. Wednesday I toured the Kennedy Space Center Visitor Complex; I'll write about that separately, except to mention the highlight, a Saturn V. Wednesday night I met two of the "tweeps", Marcus and Lisa, for dinner. There was something remarkable here that occured the whole time I was here in Florida: people from all walks of life drawn together by their fascination with spaceflight. We were like the people in Close Encounters of the Third Kind, drawn to Devil's Tower to see the landing. But this was for real!

Six of us met in front of the closed hotel lobby at 0245 and carpooled to Kennedy. We left early, expecting traffic, and arrived at our badging spot long before the NASA folks. The badging location was a small cinder-block building whose fixtures came from the era of Project Mercury. I asked around but nobody knew its history.

Our bus showed up and we boarded, every seat full. People were brisling with camera gear, but the NASA reps, Stephanie and Beth, suggested that we not take pictures because the whole thing would happen so fast. NASA has better photographers than me.

NASA provided an orbiter processing engineer named Chris (didn't catch his last name) who described the landing process, between-launch activities, plans for the decommissioned orbiters, and the like. I was familiar with a lot of this due to my voracious reading, but it was great to hear it from someone who had done it.

As you know, I have mixed feelings about simulations, but I can't access the shuttle or the Shuttle Training Aircraft, so I had been simulating the approach and landing using F-SIM, an iPad app that is reputed to be quite accurate. Atlantis would approach from the southwest and fly a Heading Alignment Cone to land on runway 15, and F-SIM allows a similar approach, complete with recordings of the dialog between the crew and Johnson Space Center ("Houston"). I know from watching the PLT camera view through the HUD during landings that the final portion is very realistic.

After Atlantis's deorbit burn the bus started taking us to the airfield. There was a little bit of a traffic jam but we got to the field in plenty of time. We were near midfield, and I had to make a quick choice, close or high? I chose close and stood at the rope.

Here's a google map screen capture, showing where we were on the field. Large screens were set up showing NASA-TV and we could hear the dialog between Atlantis and Houston. (This isn't special, I do this at home. But I wasn't at home, was I?)

It was before dawn, which was a good thing and a bad thing. Since Atlantis and the ISS were in the same orbit, it passed overhead about 9 minutes before the landing. I've watched the ISS dozens of times, but somehow this view was special. I was the first person in my part of the crowd to spot it, and everyone clapped.

The voice from Atlantis was calm. "It looks like we just passed over the Yucatan Peninsula," it said, "We wish more of you could see this."

"Atlantis, Houston," came the calm voice of the CapCom, "We show you crossing the West Coast of Florida."

Even astronauts get lost.


The double sonic boom announced that Atlantis had decelerated below Mach 1. It wasn't as loud as I had expected, but it was shaarper, more like a piar of cannon blasts. We all strained our eyes to see it passing overhead in the night sky.

This is where the sim came into play. "Atlantis, Houston, you're on at the 180." Just like the simulator app! This meant that Atlantis was on downwind, at proper altitude and airspeed, a few mile north of KTTS. I knew where to look. Nothing.

"Atlantis, Houston, you are on at the 90." OK, they're descending through 16,000. I know what they see.

"Field in sight, Houston."

What? What? The crowd around me didn't get this, and I explained.

Now they were at about 13,000 and turning final. The HUD was showing them an extended centerline, and they were steering off PAPIs calibrated to their steep glideslope.

We saw nothing. Everyone seemed to lean toward the final approach course. It was like the final minute of a tied Stanley Cup final.

"Pre-flare." OK, they're passing 2000 AGL.

Still nothing.

Suddenly a shadow passed through the floodlights illuminating the runway. I shouted something incomprehensible, and felt the electricity passing through the crowd.

"Main gear touchdown."

Still nothing in sight! The crowd was cheering.

The drag chute appeared above the bushes, and all of a sudden THERE IT WAS, still moving fast. As it passed out of sight the drag chute stayed attached, and by the sim that means that they were still moving at more than 100 knots.

This felt familiar, but I can't explain why. It reminded me of a very low approach (1/4 mile) I'd flown in a King Air, which wasn't scary until I saw the 1000 foot markers at the far end. Gotta stop!

It's a cliché, but the sight was awe-inspiring.

We reluctantly drifted back onto the bus as dawn broke, people stopping on the stair for a last look at the tower and the airfield. The orbiter was out of sight. We rode back to our cars. Everyone was bittersweet: we had seen an amazing thing, but a magical era had ended on our watch. We lingered in the parking lot, took pictures of our new friends, and headed back to the hotel to try to get some sleep.

I don't know about the others, but I couldn't sleep.

But the shuttles will.

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Wednesday, July 13, 2011


I haven't heard anything but "in line for review" from the FAA medical folks, but that doesn't end all aviation activity.

Saturday I helped the nice people from EAA chapter 1114 (Apex, NC) with a Young Eagles rally at Siler City, NC. The kids got 59 rides. I was ground crew, of course, but I couldn't help but wish that Claude B. needed a break flying the beautiful Ercoupe his grandfather bought new. Man, does he have stamina!

When I say 'grounded' I mean it in the colloquial sense of "at peace with the world and making a positive contribution."

The thing is, even without word from the FAA, I still have Sport Pilot privileges. My medical expired, it was not revoked; nor was there cause to revoke it. So I could have done it!

And tomorrow I will. My friend Richard owes me some time in his 'Coupe. Being a Sport Pilot really is a privilege.

Sunday, July 10, 2011

Crepuscule with Nellie

Before we had METARs, we had SAs. If I remember correctly, SA stood for Sequence Advisory; by the same token, a PIREP was a UA, or Unsolicited Advisory. SAs appeared on yellow paper on a teletype machine at the Flight Service Station (that's an honest teletype, not the new-fangled KSR-33). They came up in order: Pittsburgh, Harrisburg, Wilkes-Barre, Philadelphia, and so on; you could watch a cold front move across the country.

When we switched to METARs the RMK field became more formalized, and human weather observers lost the ability to put CREPUSCULAR RAYS in the comment section. Presumably the machines don't notice.

Crepuscule means twilight. I didn't learn the word "crepuscule" from a sequence report; it comes from this song by Thelonius Monk. Here Monk and John Coltrane perform Crepuscule with Nellie at Carnegie Hall. The song combines dissonance with poignancy.

My made-up explanation for crepuscular rays is highly humid air, which glows red at crepuscule, and towering cumulus to the west blocking some of the sun's rays. So the rays are actually the absence of the Sun's rays.

Seeing that remark in the SA reminded me of every evening I ever spent outdoors in the South or Plains. Crepuscular rays meant spitting watermelon seeds, fireflies, an AM radio in the distance tuned to a minor league baseball game, and maybe holding hands with a new girl.

And besides inducing nostalgia for my Taylorcraft, crepuscular rays meant something about the weather. Towering cumulus to the West in the mid-latitudes of the Northern hemisphere usually come your way, and seeing them at sunset, when things should be calming down for the day, means that those CU have lots of energy. Crepuscular rays are a poison flower, pretty to look at but...

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Saturday, July 2, 2011

Arc en Ciel

[I prefer writing about flying to writing about me, but this is an unusual juncture so please indulge me.]

For some reason the date was memorable: May 5, 1992. My third class medical certificate was expiring, and that day I got a second class certificate. The way things work in the USA, flight privileges are tied to the medical. For commercial privileges, one needs a second class certificate; for Airline Transport privileges, one needs a first class.

I got my commercial certificate in an old Cessna 210, the kind with struts and a hydraulic system so ancient that it took significant strength to position the valves to raise or lower the landing gear. An ag plane cut me off in the pattern and the examiner seemed to think that the required emergency was covered. I was a Commercial pilot.

I worked my way up, earning a bunch of certificates: multi, CFI, CFII, MEI, Commercial glider, CFI-G, and, most important of all, ATP (which took two tries, the only one that did so). For that I needed a first class medical (technically a third class will do to take the test, but you need a first class to use it), and after my double bypass in 1998 I kept my first class medical certificate, hoping for a jet job (jet captains under 14CFR135 must have an ATP, hence need a first class medical). Since I wasn't using it I let it lapse to a second class for the second six months, but during that first six months I endorsed a lot of logbooks with "ATP" rather than "CFI", instruction in commercial operations being an ATP privilege.

I flew freight, fires, and frightened patients all over the West. There is no possible universe in which a part-time pilot who is also a mathematics professor with heart disease can fly a King Air, but I got three years in King Air 200s anyway.

Two more cardiac interventions cost me the King Air, and I gave up on the jet idea and, as a consequence, on the first class medical. But I kept the second class and my commercial privileges. ATP was now a diploma on my wall and an attitude toward flying, but not something I used.

A year ago, after the incident described here, the FAA's annual letter describing what it would take to renew my second class medical became draconian: they were demanding much more testing, testing that neither my insurance company nor wallet could justify. AMEs tell me this level of testing won't be required for a third class medical.

My second class medical certificate expired June 30, and I have informed the FAA that I will not seek another (see above). The FAA is concerned about my heart, but without Rheumatoid Arthritis I would have the energy to make enough money to pay for the heart testing. And now there's evidence connecting RA and heart disease. Since my heart disease is unusual (no risk factors, no lifestyle changes, no symptoms: the only effect is that every now and then they take all of my money), it may have been RA all along.

In other words, I am a Private Pilot now. (I'm still a CFI; that's teaching, not flying.) I even changed my blog profile to say former professional pilot.

Make no mistake about it: I am proud of my PPL. In the next few months I'll write about the joys and adventures being a PPL can bring. I'm hoping for at least one long trip, and maybe a seaplane rating.

And I still intend to fly like an ATP; I have some things to say about that, too.

ps I have started a Google AdSense account, which is supposed to target ads based on content. I hope you don't mind; it seems unobtrusive to me, and it would really be nice to get a little compensation for all of this writing. I noticed in looking up the post on my most recent stent that AdSense came up with ads for heart surgeons. Now that's targetted!

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