Monday, April 30, 2012

Book Review: "Into the Teeth of the Tiger" by Donald S. Lopez

Some time in the late 1920's young Don Lopez, not quite four years old, was taken by his parents to see a parade. He sat on a Brooklyn curb for a long time, amid a throng of people. Then...
"I was caught by a surge of excitement, stood up, and waved at a man in an open car to the accompaniment of loud cheers of 'Lindy! Lindy!' Time has erased other details of that incident, but the image of that handsome, heroic figure has stayed with me. I cannot remember a time since when I was not interested in flight."

It was the air age, and an air minded youngster could go to the movies to see Hell's Angels and Wings, could read pulp magazines like Battle Birds and G-8 and His Battle Aces, and could go to Floyd Bennett Field to see Northrop Gammas and Curtiss Condors, Wiley Post's Vega and Amelia Earheart's Electra. Don Lopez did all of these things. And he scrounged an occasional airplane ride from a barnstormer friend of the family who had a WACO cabin biplane.

His ardor for aviation didn't cool when his family moved to Tampa, FL in 1939 and settled under the traffic pattern for Drew Army Airfield. There he could watch the military aviators in their P-39 Airacobras and vow that someday he'd fly a P-39 – a promise he was able to keep.

After graduating from high school in June 1941, he entered the University of Tampa as an engineering student. There was a war on in Europe and the previous year President Roosevelt had, famously, called for the production of 50,000 airplanes. The Army had no idea where they would get 50,000 pilots, and so the Civilian Pilot Training Program (CPTP) was begun. Flight training was offered to college freshmen and Don Lopez surely didn't need to be asked twice. He completed the 35 flight hours and the written test needed at the time for a Student Pilot Certificate and in the fall of 1942 he joined the Army's flight training program. Like so many of his peers he progressed through a succession of increasingly demanding aircraft – from the Fairchild PT-19, to the Vultee BT-13, to the North American AT-6. In May of 1943 got his wings, and orders to report to Tallahassee for advanced pursuit training.

Lopez writes that he was a bit disappointed to be assigned to a unit flying the Curtiss P-40N Warhawk. The more modern P-38's and P-51's had beckoned, but the venerable P-40 was to be his ride and he came to appreciate it. He learned instrument flying, night flying, formation flying, air-to-air and air-to-ground gunnery, and combat tactics. The pilot was becoming a fighter pilot.

There was lots of time for aerobatics and simulated combat, which the pilots referred to as "rat racing", and writing a half century later, the author recalls the elation:

"All in all, the hours I spent rat racing above central Florida were some of the most enjoyable of my life, especially among the cumulus clouds that usually formed in the afternoons. Diving, in trail, into the dark valleys between the clouds, and then zooming up over the bright, sunlit, towering hills, only to roll inverted to hurtle down the other side, was pure joy and I wished it could go on forever."

In September of 1943, Lt. Lopez and his fellow fledgling fighter pilots were pushed out of the nest and sent off to war. Some went to Europe, some to the Pacific, and some – including the author – went to the CBI, or China-Burma-India theater. The trek to war was long, across the South Atlantic and Equatorial Africa, and pausing in Karachi, India. There, pilots being rotated out of combat and headed back to the USA flew with the incoming replacements for a time, to try to transfer some of their hard-won understanding of combat flying in the hope of increasing the younger fliers' odds of survival.

After two months of this, in November '43, the author was ordered, to his great satisfaction, to report to the 14th Air Force in China. He joined the 23rd Fighter Group, the unit that had been created from the remnants of Gen. Claire Chennault's AVG (the famous American Volunteer Group, or more popularly, the "Flying Tigers"). The group was commanded by the legendary Lt.Col. David Lee "Tex" Hill.

After a long flight across the Himalaya's (the famous "Hump"), the fliers arrived in Kweilin, met (and were impressed by) Tex Hill, and were dispersed to front-line squadrons. Lt. Lopez would fly with the 75th Squadron based at Hengyang. After thirteen months of training and preparation, he would finally get to fly a P-40 toward the enemy and fire shots in anger.

The first combat missions that the author describes were air-to-ground strafing runs. The 14th Air Force was trying to interdict the logistics of the Japanese Army, in support of Chiang Kai-shek's Nationalist troops, and so they flew low over roads, rails and lakes and shot up trucks and trains and boats. In this, they were terribly effective:

"We continued attacking the boats, essing across them as we strafed until all the boats were burning or sinking and everyone on the decks appeared dead. It was awesome to realize that a slight pressure by my right forefinger was the difference between life and death for the soldiers on the boat. I felt no compunction, since I, along with the rest of the country, was totally convinced of the need to defeat Japan. These were, after all, the ones responsible for Pearl Harbor, the Bataan Death March, and numerous other atrocities that began, incidentally, here in China.

Killing from the air is impersonal. The pilot shoots at small moving figures several hundred yards away. Except for seeing them fall, like toy soldiers, there is none of the bloody evidence of death that one would see in close ground combat."

It would be June of 1944 before the author recorded his first air-to-air "kill", which he describes thusly:

"I immediately broke hard right, jettisoned my belly tank, and headed for the Oscars. As we approached, the Oscars broke up and went in all directions. I lined up one, but just as I got within range he flipped into a tight turn, and I couldn't get enough lead to fire. I rolled over and saw an Oscar below me. I dived after him, and he went into a tight right turn. I wouldn't have been able to hit him, but he suddenly reversed his turn, and I nailed him before he could turn in the opposite direction. I must have killed the pilot, because he went into a gradually steepening dive without any evasive action.

... It was satisfying to shoot down an enemy fighter... Air-to-air combat is what every fighter pilot is trained for, and even though ground attack is dangerous and important tactically, it doesn't come close to air combat for exhilaration and satisfaction."

Ultimately, Don Lopez would score four aerial victories in the P-40 and one later in the P-51, making him an Ace. Throughout the book, he writes approvingly about the Warhawk. This is a marked contrast to the views of another notable fighter pilot, Col. Jim Morehead. In his book, In My Sights, he expresses neither affection for nor trust in the Curtiss fighter. But Jim Morehead flew and fought in the Dutch East Indies in the dark days of early 1942 and this is likely to have colored his thoughts. On the other hand, Don Lopez says of the P-40:
"We were proud to wear the mantle of the Flying Tigers and continued to use the tactics developed by General Chennault for them with great success. We used the strengths of the P-40, diving speed and rugged construction, to overcome the maneuverability of the Zeros and Oscars. We always kept up our speed and never tried to out-turn a Japanese fighter. If one evaded us with a tight turn we just kept diving, then climbed up and attacked again."

On the 4th of August 1944, Don Lopez made good use of those strengths of the P-40 in a memorable fashion. He had been strafing enemy units at low level and had exhausted his ammunition. While climbing back to higher altitude...

"...I spotted a bunch of Japanese circling over Hengyang. We headed toward them and saw that there were twelve Oscars covering six or eight Aichi D3A Val dive bombers that were attacking Hengyang...

As we closed on them Quig instructed everyone who was out of ammunition to go home and told his flight that he was going down after the Vals. I signaled my element leader to take the flight home. They peeled off to the south and I went after the Oscars. I figured that Quig's flight could use some help in keeping the Oscars off them and that the Japanese couldn't tell that I was out of ammunition.

I made a diving head-on pass through the Oscars and they scattered like birds in all directions. When an enemy fighter is diving on you, the last thing you do is try to see if he is firing at you. Break first, think later, is the rule."

The author continues his description of the episode and notes that his buddy Quig and crew, unmolested by the Oscars, shot down several of the dive bombers. For his role that day, Don Lopez was awarded the Silver Star.

The stories go on, as the author recounts his path to 100 combat missions. At that time, 100 missions got you rotated back to the States for leave and eventual reassignment. And so as 1945 began, Don Lopez was off combat status and awaiting his orders for home. Here, the story includes a vignette titled, "A Warrior's Mercy", and of it the author says, "On January 19, 1945, I played a small part in a drama that was as tragic as anything William Shakespeare ever wrote." It is plainly written and powerfully affecting.

Don Lopez began the long journey home in February, stopping again in Karachi but this time as the trainer, not the trainee. It was early May of 1945 when he arrived in Miami. A month later he was at his new assignment as a test pilot at Eglin Field in Florida. He'd spend the next five years there, testing the early jet fighters.

Into the Teeth of the Tiger is Don Lopez' story. The book does not list a co-author, there is no "as told to...". The voice is authentic, the details are precise and the feelings for adventures survived and comrades lost are sharp and true. This is a splendid book.

After his retirement from the Air Force, Don Lopez became Deputy Director of the Smithsonian National Air and Space Museum. He went West on 3 March 2008, aged 84, and is buried at Arlington National Cemetery.

Tuesday, April 24, 2012

Interesting at Both Ends

The flight yesterday morning from KVKX in the DC area to KBDR in Connecticut was interesting from start to finish...except for the middle, which was uneventful. The departure was interesting due to the potential for icing (in late April!) and the arrival was interesting due to the approach conditions.

On Sunday I paid close attention to the forecast for temperatures aloft at 11Z the following morning (my planned departure time). Notably, the 0°C isotherm would be running just about north to south over the DC area at 3,000 and 6,000 feet. This was the leading edge of a vast pool of frigid air being rotated cyclonically around a deep low pressure center that would be over northern New Jersey (see the (click to enlarge) chart above left, a surface analysis for 7 AM EDT on Monday).

So a successful departure would involve staying low and dashing to the east with the expectation of finding considerably warmer air over the DelMarVa peninsula. Then I could climb to a reasonable en route altitude (I'd filed for 5,000 feet).

The next morning the surface temperature at KVKX was 40°F (about 4.5°C) when I got there at 0600. By 0700 N631S and I were at the hold short line for Runway 24 and I called Mount Vernon Sector for my release. They gave me four minutes to be off and stipulated, "Climb and maintain 2,000 feet; enter controlled airspace on a heading of 180°." We were off.

At 2,000 feet the outside air temperature (OAT) was 34°F as the Potomac TRACON controller said, "Cessna 31 Sierra, turn left heading 090, climb and maintain 3,000." My reply was, "Potomac, 31 Sierra left to 090 and I have a request on the altitude."

She asked me what I'd like to request and I said that I was in IMC and just about at the freezing level – so could I please continue to the east at 2,000 until I reached some warmer air. The controller cleared me to maintain 2,000 feet and said I should let them know when I wanted higher.

As I approached the western shore of Chesapeake Bay (by this time cleared direct to the Smyrna VOR (ENO)), the OAT was up to 37° so I requested 3,000. The temperature there was 35° and I could see that a few miles ahead there was a gap between layers with the overcast well above me. Since it would be nice to have some additional altitude in the bank crossing the Bay, I asked for and got my final altitude of 5,000 feet. At top of climb the temperature was still in the mid 30's and from then on it just got warmer.

I'd pulled ahead of the advancing cold air, and soon N631S and I were on top in the relatively warm sunshine. This was the uneventful "middle" of the trip, so I could use the time to plan for the arrival at KBDR. I'd had a look at the weather Bridgeport was reporting prior to departure; it had been moderate visibility in mist and a 500 foot overcast ceiling with light winds out of the northeast. The ILS approach for Runway 6 would be on offer so I dug out the approach plate and clipped it to the yoke. Then I pulled up the latest METAR and got a bit of a surprise. The ceiling had lowered to 300 feet:
KBDR 231049Z 02012KT 10SM OVC003 11/08 A2919 RMK AO2 RAE0956
The Decision Height for the ILS Rwy 6 at KBDR is also 300 feet...so unless things improved this approach would be to minimums. That was fine, but I'd be a lot more relaxed if it was a couple hundred feet higher!

N631S and I continued north along airway Victor 16 toward JFK, helped along by a nice tailwind that kept ground speed up around 155 knots. Another METAR came up about 1200Z:

KBDR 231152Z 15008KT 8SM OVC005 12/11 A2922 RMK AO2 SLP894
OK, better. The wind, still fairly light, had veered to the southeast (150008KT) and the overcast was up to 500 feet again. I relaxed and picked up the ATIS broadcast (which was by now in range). It confirmed the numbers from the METAR and added, "ILS Runway 6 in use, landing and departing runways 6 and 11." That meant a "circle to land" option was available.

"Circle-to-land" is used when approach conditions dictate use of an instrument approach to a runway that is not suited for landing. This could be due to adverse winds, or to a runway closure. Approach plates have separate minima for straight-in and circling conditions, the latter being a bit higher.

A "circle-to-land" approach can be tricky, depending on conditions. You're maneuvering, usually well below normal pattern altitude and often just below an overcast. It might be windy, it might be raining, it might be dark. There have been nasty accidents and many air carriers restrict the use of circle-to-land in their procedures. It's really a rather rare event – as of yesterday I had never made use of circle-to-land.

Checking on with the final New York Approach controller, I said, "New York Approach, Cessna 631 Sierra, level 3,000, 'Papa' at Bridgeport." and he said, "Cessna 31 Sierra, Bridgeport altimeter is 29.22. Will you want the circle to Runway 11 or the straight in?"

I was all set for that question. With the wind from 150° at 8 knots it was a direct crosswind well within N631S's capability. I saw no reason to mess about with the circling approach and told him I'd take the straight in.

A couple of minutes later, I was in the clouds at 2,000 feet above the Sound and approaching the localizer. Approach cleared me for the ILS and handed me off to Bridgeport Tower with whom I checked in: "Good morning, Bridgeport Tower, Skylane 631 Sierra on the ILS 6, 2 miles outside STANE, inbound for landing." The tower controller then threw me one more curve.

"31 Sierra, Bridgeport, report STANE. The wind has shifted to 170 at 9 knots, I was going to offer you circle to Runway 24...do you want that?"

I thought about that as I continued down the glide slope. A wind from 170° was beyond a direct crosswind and would give me a tailwind component. A slight one, but even so... I didn't yet know where I'd break out of the overcast; circling at 300 or 400 feet was not an attractive proposition. So I said to Tower, "I'd like to decide when I break out, depending on conditions."

He responded, "OK, that should be about three miles out, let me know your intentions." "31 Sierra, Roger."

At the end, I descended out of the cloud base at about 600 feet, into good visibility. I told the tower, "31 Sierra will circle to land 24."

"You can circle North or South, your choice."

"31 Sierra will circle south of the field." Circling to the south resulted in essentially making "left traffic"; this made it easier to keep the runway in sight at all times. And so I motored around at 500 feet altitude, which made for an interesting view. The only "burble" came when I turned to the North (essentially, turned onto base) and went from 10° to 20° of flaps. The added lift (along with some inattention on my part, I fear) popped me up into the base of the overcast. I quickly pulled some power and pitched down to stop the unintended climb, and got back down into the clear. A good lesson on how circling approaches can quickly become "interesting."

The subsequent landing was routine, and I got to log another 'first', a circle-to-land approach.

Saturday, April 21, 2012

Lift is Temporary; Gravity is Permanent

Yesterday about 2020Z, Cessna 631 Sierra and I were motoring along on a 270 heading at 8,000 feet MSL somewhere north of White Plains (KHPN) and east of the Hudson River. We were talking to New York Approach on 120.8 MHz. That's about when I heard an exchange involving an eastbound Bonanza – 1 Sierra Mike – at 7,000 feet (N.B. – all quotes from memory, some paraphrasing inevitable):
1SM: "Approach, Bonanza 1 Sierra Mike, we're going to need a vector to the nearest airport."

NY Approach: "What was that? 1 Sierra Mike, you need to go to an airport?"

1SM: "Yes, we're having some engine problems and we're going to need to land."

NY Approach: "OK, that'll be White Plains. 1 Sierra Mike, turn right to a heading of 240 and descend and maintain 3,000 feet. You can expect the visual to Runway 16 at White Plains."

1SM: "OK, right turn to 240, descend to 3,000, 1 Sierra Mike."
Am I the only one that has a couple of problems with that? Hold the thought while I continue here.

After a couple of minutes...

1SM: "New York, 1 Sierra Mike, can you tell me where the airport is?"

NY Approach: "The airport is about 9 miles at your 10 o'clock now."

1SM: "OK, we don't see it; I guess we want to try to stay a little higher here..."(sic)

NY Approach: "1 Sierra Mike, altitude your discretion, the airport is about 8 miles now at your 9 o'clock. Turn left to 180."

1 SM: "We're having trouble holding altitude here. I'm not sure we're going to make the field."
Here, courtesy of FlightAware.com is the ground track of 1 Sierra Mike, beginning with departure from Teterboro (KTEB):

My inference is that the controller had 1 Sierra Mike on a left base for Runway 16 at KHPN and planned to turn him onto the localizer somewhere around the usual intercept gate for IFR approaches. (As usual, click to enlarge. Bonanza 1SM is the blue track.) Unfortunately, 1 Sierra Mike was running out of altitude before that plan could be accomplished. Meanwhile, the riveting exchange continued on the frequency...

NY Approach: 1 Sierra Mike, say souls on board and, er..., fuel."

1SM: "It's the two of us on board and we've got one full tank and the other side is about half."

1SM: "Approach, 1 Sierra Mike is definitely not going to make the field. We're going to put it down out here. There's a field and a road over to the right."

NY Approach: "1 Sierra Mike, radar contact lost."
A minute or so later, an Emergency Location Transmitter (ELT) signal began on 121.5 MHz, the emergency frequency. 1 Sierra Mike was presumably on the ground, and had decelerated abruptly enough to trigger the ELT.

Again courtesy of FlightAware.com, here are the altitude and speed profiles for 1 Sierra Mike.

Quite soon thereafter N631S and I were handed off to the next sector, but I tuned the number two radio to 120.8 and kept monitoring. Soon, several aircraft, carefully separated by altitude, were looking for 1 Sierra Mike's location. One searcher posed a question:

Search Aircraft: "New York, what's the type aircraft and color?"

NY Approach: "It's a BE36...I guess we don't know the color."
After perhaps another five minutes, the controller said to one of the search aircraft, "Thanks for your help, you can continue. Somebody found them over there."

When I arrived at home in the DC area I quickly looked for news of the incident on-line and was rewarded with a brief article that referred to a "forced landing" and, more importantly, did not mention injuries or worse.

This, to me, is a beautiful picture. They may not get to use that airplane again, but it shows a controlled touchdown and a survivable event. The pilot, who had sounded very calm throughout, clearly kept his composure, chose a viable emergency field, and executed a good off-airport wheels-up landing.

This morning, I learned from updates to the news item, that the two on board were transported to the hospital with injuries judged to be not life-threatening. So the outcome, basically, was good. And that leaves open a question: Why am I troubled by this incident?

Let's start with a disclaimer: I'm not a qualified accident investigator. I am typically appalled by speculation in the aftermath of accidents. I guess I'm about to do that which usually annoys me. Well, here goes...

  • First, the pilot – who really did a great job throughout this incident – erred, in my view, by not using the E-word on the first call to approach after the engine went bad. His phraseology was ambivalent and the seriousness of the situation was not at all clear. It costs NOTHING! to say, "Bonanza 1 Sierra Mike is declaring an emergency due to loss of power." Doing so removes all doubt from the minds of the ATC people.
  • Second, the controller treated the situation like a normal approach into KHPN. He issued a descent to 3,000 feet (to get below KLGA arrivals?) and pointed the airplane toward the 16 localizer. The pilot didn't declare an emergency, and the controller didn't treat it as one. If the initial vector had been directly to the numbers at KHPN Runway 16, would 1 Sierra Mike have made it?
  • Third, the controller issued a descent to three thousand and the pilot knew his engine was in trouble. The best one word response would have been, "Unable!" Instead, he started down. With the engine questionable (or worse), altitude is your bank account. You don't give it up without a really good reason. It seems that the pilot ceded command authority to ATC...never a good idea.
  • Fourth, even as it became clear that an emergency had developed, the controller asked for "souls on board" (good!) and "fuel" (why?). In the moment, it would admittedly be hard to do the logical thing – ask for the color of the airplane that is about to be on the ground – but that just emphasizes the rote nature of the responses. Perhaps ATC needs a better training module for dealing with emergencies.
I would ask a favor from all who read this. Please don't think that I'm condemning the pilot or the controller in this incident. They both did well given the circumstances, and the people on the airplane will, it appears, be OK. But I believe there are lessons here. I've taken them aboard and I hope others will, as well.

Wednesday, April 18, 2012


On this date seventy years ago – 18 April 1942 – 80 men led by Lt. Col. James H. Doolittle launched from the aircraft carrier USS Hornet in sixteen North American B-25 Mitchell bombers to turn the violence of war back upon the Empire of Japan.

Of the 80 men who departed Hornet on what became known as the Doolittle Raid, 69 returned (five are still among us). Their audacity, their professionalism, their unmatched courage inspire to this day.

The President of the United States
in the name of The Congress
takes pleasure in presenting the
Medal of Honor

(Air Mission)

Rank and organization: Brig. Gen'l, U.S. Army Air Corps.
Place and date: Over Japan.
Entered service at: Berkeley, Calif.
Birth: Alameda, Calif.
G.O. No.: 29, 9 June 1942.

For conspicuous leadership above and beyond the call of duty, involving personal valor and intrepidity at an extreme hazard to life. With the apparent certainty of being forced to land in enemy territory or to perish at sea, Gen. Doolittle personally led a squadron of Army bombers, manned by volunteer crews, in a highly destructive raid on the Japanese mainland.

Sunday, April 8, 2012

A Long-Term Relationship

The trip from Connecticut to the DC area on Friday had something to offer and a price to be paid. On offer was a perfectly clear sky – not a cloud to be found – and an unusual (for the route) tailwind out of the north. The price of admission was fairly continuous light turbulence (and occasionally not so light) up to 8,000 feet.

The photo at left was taken approaching the Hudson River at Croton-on-Hudson from the east. There's a little haze, but looking past the Tappan Zee Bridge you can discern the George Washington Bridge and the upper reaches of New York Bay. That's about 40 miles distant.

Soon after that picture was snapped, after reaching the Sparta VOR (SAX) and turning south, N631S's tach time rolled to 4,245.0 hours. Not a terribly "round" number, but one that I took note of. Back on 27 September 2004 (about seven and a half years ago) when Bob Parks and I departed Keokuk Muni (KEOK) for the flight back to Connecticut, the tach read 3,245.0. That was my first flight in N631S as its ninth owner, and as of Friday last, the airplane and I have flown 1,000 hours together.

Among the owners who've had the privilege of caring for N631S, I've had the longest tenure in calendar time at 90 months (and counting). In terms of flight time I'm in second place, about 200 hours behind the pilots at Erect-a-Tube, Inc. (Shout-out here to Sam F.!) At the rate things have been progressing, I ought to catch up in a bit over a year.

After a thousand hours, you get to know an airplane. I don't recall the last time N631S surprised me. Its responses are predictable and stable. It does everything fairly well and some things brilliantly, and it never bites. I'm grateful to Dwane Wallace and his colleagues at Cessna for a wonderful bit of airplane design.

While it is always risky to indulge in prediction, I suspect – and hope – that N631S and I will be together for a long time to come.

Wednesday, April 4, 2012

2012 Annual Inspection (viii)

And so, inevitably, the bill has arrived. And as in prior years (2011 here, 2010 here, 2009 here) we can separate it into a number of "chunks" to better understand where the money goes for an event like an Annual.

As discussed in the first post of this series, I agreed to a flat-rate payment of $2,657.40 covering the actual inspection of the aircraft and the basic preventive maintenance items that normally accompany it. We start from there.

Four work items added significant cost to this maintenance event. They were:

  • Replace right elevator and stabilizer tips; replace failing right elevator spar rivets. The labor expended on this set of tasks was 7.1 hours at $86.00/hr. or $610.60 total and the cost of parts (primarily the plastic tips) was $287.44. Total cost = $898.04.
  • Replace the muffler. Labor to disassemble the exhaust system, remove and replace the muffler, and reassemble, was 6.1 hours, $524.60. The new muffler's cost was $357.95. Total cost for the work item was $882.55.
  • Perform 500 hour service on both magnetos. The labor cost was 3 hours for each mag, or $516.00 for both. The right mag needed a new distributor block ($363.43); the left mag needed points ($52.95), a carbon brush ($6.54) and a capacitor ($143.34). Total for parts was $566.26 for both mags; total parts and labor for servicing both magnetos was $1,082.26.
  • Replace one worn seat roller housing. Labor of 0.7 hours, $60.20; cost of the part, $519.10. Total $579.30.
The total cost for these four items was $3,442.15. Adding this to the flat-rate package I'm up to $6,099.55.

Additionally, there were a number of items that added up to another significant cost element: Replace alternator noise-supression capacitor ($93.99); Restore damaged paint on engine mount ($111.80); Remediate main landing gear corrosion ($129.00); Replace the brake linings ($247.32); Research logs for AD compliance, etc. ($318.20). Total for these = $900.31. So far, up to $6,999.86.

An assortment of minor items (clear a chafe here, stop drill a crack there, etc.) added in aggregate $692.55. The running total is now $7,692.41.

Finally, adding the post-maintenance run-up, cost of oil, shop consumables, inbound freight charges for parts, and the Airport Use Fee – together $595.42 – gets us to the total cost of the maintenance activity: $8,287.83. In today's market and based on N631S's equipment and condition, I'd estimate that to be in the neighborhood of 7.5% of the value of the airplane. As an annual maintenance cost for a 35 year-old machine that's acceptable.