Saturday, July 31, 2010

Book Review: "The Engines of Pratt & Whitney: A Technical History" by Jack Connors

There is a soft spot in my heart for Pratt & Whitney Aircraft. In the mid-1960's when I embarked on my engineering education the aerospace industry was booming. We were going to the moon! Four years later there was a recession on. Apollo was winding down, Southeast Asia was hot, and job offers were scarce. I went to work for P&WA, assigned to design small bits of turbine engines.

The job lasted ten months; then they allowed as how I could keep coming to work but they couldn't afford to keep paying me. I moved on, soon ending up in the shipbuilding business.

But what I'd seen of engineering as it was practiced at Pratt & Whitney, I'd liked. They were an organization committed to giving the customer a product that was first class in every respect, and they applied leading-edge technology to do it. I learned a few good lessons in my short tenure there.

Now, Jack Connors' new book has provided a context for my experience. Mr. Connors joined P&WA in 1948 as the piston engine era was drawing to a close and he retired as a Vice President in Engineering, in 1983. After retirement, he and a couple of colleagues invested thousands of hours in organizing and indexing the company's engineering archives. That effort provided the source material for this book.

Much of the book is concerned with what Mr. Connors regards as P&WA's four "defining moments":

  • The founding of the company (1925)
  • The WWII effort (1939-1945)
  • The transition to turbine power (1947-1958)
  • Winning the F100 engine program (1968-)
R-4360 Wasp Major
The author uses many first hand accounts to bring these "moments" (several of which stretched over years) to life. We learn how and why Frederick Rentschler started the company and how George Mead and Andy Willgoos inspired both the design brilliance of the great radial engines and the incredible industrial effort that saw P&WA engines supply 50% of the installed horsepower in the WWII aircraft fleet.

We learn, in a really suspenseful sequence, how the company started the gas turbine era desperately far behind GE and Westinghouse, and how Luke Hobbs and Perry Pratt led the engineering effort that produced the J-57 engine for Boeing's B-52 Stratofortress - an engine that represented both a "bet the company" program and a quantum advance in turbojet performance.

The J-57 in its commercial guise (as the JT-3) went on to power both the Boeing 707 and the DC-8 (and the rest, as they say, is history).

TF-30 Afterburning Turbofan
And, in the usual manner of technical evolution, the J-57 turbojet led to the TF-33 turbofan (power for the C-141 Starlifter), which was scaled down and provided with an afterburner to produce the TF-30 that occupied my time for a year. And the TF-30 (power for, among others, the F-111 and the F-14 Tomcat) was the parent of the F-100 that went into the F-15 and F-16 and led to other advanced engine programs.
JT-9D High-bypass Turbofan

While one must respect the author's conclusions, I'd have proposed the development (well described here) of the JT-9D high-bypass turbofan during the same years that the F100 was evolving, as a much more significant milestone. The JT-9D powered the first Boeing 747's that arguably revolutionized commercial air travel, and its technical "DNA" can be seen in every large airliner turbofan to this day.

Mr. Connors' book provides only an overview (certainly an interesting one) of the piston engine era. It was before his watch, so to speak, and he paints with a broad brush and suggests other references to fill in the details. But his technical history of the first 35 years of the turbine era at Pratt & Whitney is masterful, and for that era, this will be an essential reference.

Thursday, July 29, 2010

Don't Blame It on the Weather!

James Fallows is a National Correspondent for The Atlantic whose work I enjoy greatly and respect immensely. He also happens to be a capable instrument-rated private pilot (I believe he owns a Cirrus SR-22). Mr. Fallows maintains a blog wherein he comments on matters political, cultural and occasionally aeronautical, and yesterday he offered observations on the Airbus mishap in Islamabad.

The information in the post is helpful and cogently presented...but there are a couple of paragraphs, tangential to the main thrust of the piece, that I feel require a counterpoint. He has this to say:

"Bad weather is ultimately responsible for most of what goes wrong in aviation.(*) Fog or clouds that keep pilots from seeing the runway (the Polish airline tragedy), strong or gusty winds that complicate the process of touching down, icing in below-freezing clouds (Colgan in Buffalo), severe turbulence from thunderstorms (probably the Air France flight over the Atlantic), etc. ..."

The asterisk points to this footnote:

"(*) For another time: the different genesis of commercial-airline versus private-pilot accidents, with flat-out pilot error playing a far larger part in the latter case. But there too weather makes a huge difference."

With all due respect, I disagree. Bad weather is not "ultimately responsible" for anything. Bad weather simply is!

The fog in Smolensk wasn't responsible for the accident that killed the Polish president; blame lies with poor decisions made (for whatever reason) by the flight crew. The cold, wet weather in Buffalo wasn't responsible for the Colgan Air crash; at issue was the inability of the Captain to respond correctly to the situation. We don't know what brought down Air France 447 (and may never know) but other aircraft passed through that area before and after the fatal flight without incident.

The quoted footnote seems to imply that "private-pilot accidents" differ in kind from air-carrier accidents. Certainly they differ in frequency (air-carrier accidents being far more rare). But in the vast majority of cases, across all segments of aviation, the sudden meeting of aluminum and unyielding earth is the result of carelessness, incapacity or neglect on the part of the flight crew. We, ourselves, are the greatest source of risk.

Don't blame it on the weather.

Monday, July 19, 2010

Why a High Wing is Better

This morning's first look at the weather showed quite a lot of convective activity over eastern Pennsylvania. The stuff was heading east-northeast and would certainly bear watching.

N631S and I departed Potomac Airfield at 1153Z, and about 3/4 of an hour later we were over New Jersey approaching the Coyle VOR (CYN) while wondering what that big patch of weather just west of JFK was going to do. As it turned out, it more or less left JFK alone, passing just to the north. But it headed straight for Bridgeport, our destination. This could not be classified as good news.

As we made the right turn at JFK and headed out to the east over Long Island it did not look like we could beat the weather to KBDR. The New York Approach controller checked with the tower there and advised me that there was frequent cloud-to-ground lightning just west of the field. This was no place for N631S and me.

The controller asked my intentions and I said I'd like vectors for the RNAV (GPS) RWY 2 approach at Tweed/New Haven (HVN) and if that didn't look good I'd break off to the east and divert to Groton-New London (GON). But that further diversion proved unnecessary. As the storm cell was beating up KBDR we landed uneventfully at KHVN and taxied over to the FBO's ramp to wait out the severe weather. In a few minutes it began to rain; an hour later it had passed. N631S and I made the quick hop back to Bridgeport VFR.

Oh, about the "high wing" thing. If you have an airplane with the wing on top you can sit on the ramp with the door open and enjoy watching the rain.

Friday, July 16, 2010

No Left Turn

After more than 33 years, it is unsurprising when some parts begin to show signs of wear. N631S has proven not to be immune to this, in common with all machinery. It's a pretty typical story.

We decided to take a bit of a holiday, and so on Monday last we flew from Potomac Airfield (KVKX) to Easton/Newnam Field Airport (KESN) on the Eastern shore of Maryland. We planned to stay at an inn in St. Michaels, MD and explore the environs. It all went extremely pleasantly and on Thursday morning we flew back to KVKX. Both of the short VFR flights were pleasant and uneventful.

After landing I stopped at the fuel island and topped off the tanks. As I set the brakes prior to starting the engine I felt a "pop" under the left pedal. Odd but unidentifiable. N631S and I proceeded to turn right onto the taxiway...then right onto the grass...then right behind the T-hangar row. Then we proceeded to NOT turn left (at least not much) to align the airplane with the hangar. Diagnosis: No braking on the left wheel.

I called Phil, the mechanic that I usually turn to when troubles arise at Potomac Airfield. He was backed up with work but referred me to Dan Fragassi of Clinton Aero Maintenance at nearby Hyde Field (W32). Danny got over to VKX this morning to examine N631S and here's what he found.

The two brackets that secure the bottom of the brake master cylinder for the left wheel (Items 13 and 14 in the exploded view at left) had failed. (See dead parts, photo below.) With the master cylinder thus adrift, there was no braking action on that wheel, and hence no (tight) left turns! So I'm at least in for new brackets, list price $35.90 for both. Not so bad.
But the next question is, why did the brackets fail? They seem unlikely to cause trouble if not subjected to unusual stresses. But examination of the rest of the pedal assembly suggested the source of the problem.
Referring back to the exploded view, the pedal is item 1. It rotates on a shaft, item 10, as it actuates the brake master cylinder via a clevis. The hole in the pedal assembly (1) in which the shaft (10) rotates is badly worn (see photo at left). So, as well as the brackets I need a new pedal, list price $218.00. It's a complex part with lots of machining and welding so that isn't so bad.

Then there's the shaft (10). It's bent. So I'm going to get the shaft. Yes, I mean that in a couple of senses. You'd think the part would be a simple steel pin. Ah, not so! It is a tube, about 4.00" long and 0.180" in diameter with a hole about 0.060" down the middle. One end is upset to retain the clevis and the other end is drilled for a cotter pin. List price for the shaft (wait for it...): $260.00. Ouch!

I'm going to ask around about why the shaft needs the hole down the middle and why a 79 cent solid steel pin won't do the job. I'm sure that the engineering rationale will be fascinating!


By the way, UPS is supposed to deliver the parts tomorrow (Saturday). If they hold up their end I should be good to go for the usual Monday trip back to Connecticut. Let's hope.

UPDATE: 7-17-2010: Gary from Clinton Aero Maintenance called me at 3:30 this afternoon. The parts arrived as promised and N631S is ready to go. Have I mentioned that I love Aviation Maintenance Technicians just as much as I love Air Traffic Controllers?

Sunday, July 11, 2010

Just a Little Weather

After leaving KBDR Friday evening, N631S and I were westbound, about 40 minutes out, skimming the tops at 8,000 feet.

We were approaching Sparta (SAX) and the turn to the south toward Solberg (SBJ). But I just didn't like the look of the anvil-topped cloud off to the left (photo left, above). I did not want to go there.

So, I asked New York Approach if I could continue on present heading (about 270) for 4 or 5 miles and then turn south. I got: "Approved as requested; advise when you can accept direct Solberg." Nice.

After clearing the buildup to the west, I contacted approach and asked, "Can N631S have present position, direct Broadway, direct LANNA?" I saw no reason to back-track to the east toward SBJ and more weather. Broadway (BWZ) was on-course and clear according to the XM Weather display on the Garmin GPS 396. There was some action down around LANNA but I figured I would deal with that once I switched to Allentown Approach. Well, New York Approach was way ahead of me.

I got: "Skylane 31 Sierra, you don't wanna go to LANNA. There's a big cell right there. Cleared direct Broadway for now; depart Broadway on a 240 heading. Expect direct East Texas in a few miles.

Before reaching the Broadway (BWZ) VOR, I got "31 Sierra, cleared direct East Texas", and a couple of minutes later, "31 Sierra, contact Allentown Approach on 124.45."

This track, as seen in the screen shot above, put the active cell near LANNA well to the south.
After contacting Allentown Approach, I was cleared "direct FLOAT" and enjoyed a smooth ride in and out of the cloud bases at 8,000 feet for the next 25 minutes.

After reaching FLOAT and turning southwest toward Lancaster, N631S and I were essentially out of the weather. The rest of the flight down to KVKX was a nice ride in VMC weather.
Notice the frontal weather approaching from the west! On arrival at KVKX it was still about 70 nm away and approaching slowly. It would give the DC area a good soaking during the succeeding 24 hours. But, not a factor on this flight. I'd been watching that front and its speed of advance for a day or so and was comfortable with it.

Here, at left, the full track of the flight courtesy of the nice folks at FlightAware.com.

Friday, July 2, 2010

A LAMP to Illuminate the Weather (cont'd)

I've been having a good e-mail dialogue with Rick Winther at DC Center (ZDC). It seems they've been having a bit of trouble keeping the interactive displays for the Center Weather Service Unit (CWSU) (described in the previous post) up and running. Hey, this stuff is complicated and not in any way easy!

In any event, Rick says that the Good Stuff will be up and running Real Soon Now, and offers this link for interim access while the work is completed.

These guys are doing great things for us, and I am very appreciative of the effort.