Sierra Sue II - Revealing a Combat Veteran's True Colors

Sierra Sue II Revealing a Combat Veteran’s True Colors Story by Chuck Cravens

The restoration of combat veteran P-51D 44-63675 by Air Corps Aviation has set a new benchmark in the Mustang community. From varying shades of its natural metal skin to visible Alclad logos and its crude, albeit correct, nose art, the attention to detail is extraordinary. Photo: Leo Correa Luna

10

Sierra_Sue II.indd 10

WARBIRD DIGEST #59

3/17/15 2:55 PM

T

he push to Berlin was on. Sierra Sue II joined her squadron performing strafing missions and escorting B-17s on bombing raids, clearing the way for Allied troops to secure victory. Sadly, the maiden warrior’s role in helping win the war was lost when the United States Army Air Force (USAAF) sold her as surplus soon after the conflict ended. For decades the P-51 Mustang shuffled countries and owners, her valuable history forgotten—hidden below numerous paint applications. In recent years, restoration experts scraped away the multicolored layers, revealing the true identity of Sierra Sue II.

The 9th Air Force jumped from airfield to airfield to keep up with the rapidly advancing Allied troops.

On March 7, 1945, during Operation Lumberjack, 22-year-old Lieutenant Karl H. Timmerman, commander of A Company/14th Tank Battalion, led an under-strength squad of men from the 27th Armored Infantry Battalion on an assault to capture the Ludendorff Bridge at Remagen. Seizing this bridge would allow the Allies to cross the Rhine River and continue advancing toward Berlin.

MARCH/APRIL 2015

Sierra_Sue II.indd 11

11

3/17/15 2:55 PM

While in the ownership of Dr. Roger Christgau, who is of Swedish descent, the Mustang flew in a mixture of U.S. and Swedish markings.

Photo: Dick Phillips

Photo Leo Correa Luna

The 402nd Fighter Squadron (FS)/370th Fighter Group (FG), which was part of the 9th Air Force, was assigned to support the movement of the 2nd Armored Division (AD) in the drive to Berlin. The 2nd AD was the first division to reach the Elbe River on April 11, 1945. On April 20, all British and American forces were halted at the Elbe. Berlin was captured by the Russians.

The forecast over southeastern Germany on April 25 was warm and sunny, so the 402nd FS took off on a B-17 escort mission to Erding, Germany. Just three days before, they had moved forward about 135 miles from Zwartberg, Belgium, to Y-99 near Gutersloh, Germany.

Though the pilots couldn’t have known it at the time, this attack against German aircraft marked the last day that B-17s would bomb Germany.

Lieutenant Robert H. Bohna As was typical with 9th AF squadrons the 402nd had been flying mostly tactical support missions and a chance at air-to-air combat was a pretty rare thing. So when Lieutenant Robert H. Bohna spotted three ME 262s on the way back from Erding, he left the formation without breaking radio silence and gave chase. He knew he was out of range and wouldn’t catch the revolutionary jet fighter. Bob laid the pipper of his gun sight on the distant speck anyway and pressed his trigger button. The

12

Sierra_Sue II.indd 12

gun camera clicked on, and Sierra Sue II shuddered as her six fifty-caliber Brownings rattled. After weeks of little air-to-air action, it gave Bohna a rush, even if the bullets went only halfway to the jet. (Christgau, J. (1993). Sierra Sue II, The Story of a P-51 Mustang, p. 55. Bloomington, Indiana: Xilibris Corporation.) A 21-year-old flying one of the 20th Century’s most exciting fighters can’t be blamed for having a little fun, even in the deadly serious realm of combat.

Robert H. Bohna was born in Ukiah, California, on February 12, 1924, and grew up on the family cattle ranch near Raymond, California. The Bohna place was east of the Sierra Nevada Mountain range and the family drove their cattle into the mountains in the summer to graze. They still do to this day.

Robert left college at the University of California, Berkeley to enlist in the Army on March 4, 1943. He went through the various levels of pilot training at Rankin Field in California and Marana and Chandler fields in Arizona. Bob also spent a short time at the Army Air Forces Technical School in Lincoln, Nebraska followed by the Army Air Force College training program in Cedar Rapids, Iowa.

Once training was completed, Lt. Bohna shipped off to Europe. On August 15, 1944, he was assigned to WARBIRD DIGEST #59

3/17/15 2:55 PM

Into the storm clouds of war? Not quite, but the surreal lighting of this photo does highlight the differing shades of natural metal skins of Sierra Sue II. Photo: Bob Canepa

the 402nd as a replacement pilot. At that stage of the war the 402nd was flying ground support missions in P-38s, though some bomber escort missions were flown. On December 17, 1944, the second day of the Battle of the Bulge, Robert shot down a Focke-Wulf 190 to claim his only aerial victory of the war. The squadron continued to support ground troops through Belgium and Germany. In March and April 1945, the 402nd converted to P-51 Mustangs.

After their last mission on April 25, the war was effectively over for the 370th FG and 1st Lt. Bohna, but one more notable flight occurred on May 7. At about 1020 hours, word reached the group that German forces would surrender unconditionally. The group flew an air show at 1400 hours with the planes flying in formation to spell “V E DAY.” German war operations ceased at 2300 hours on May 8.

The rest of the world found out when Winston Churchill broadcast the official announcement.

Bohna was awarded the Distinguished Flying Cross and Air Medal.

Robert went on to a long career as an airline pilot and was active in the Air Force Reserve as late as 1972. He believed that you have to stay active to remain healthy, so after the airlines he owned Sonoma Truck and Auto in Sonoma, California. Though I never had the honor of meeting him, I feel like I know Bob Bohna through all the stories and information family members have generously shared with me.

Robert Bohna died on January 21, 2010.

Looking back to the beginning, the Mustang that Lt. Bohna flew, identified as P-51D-20-NA 44-63675, rolled out of the North American Aviation plant in Inglewood, California November 25, 1944. The USAAF accepted her two days later. The Mustang was shipped overseas from Newark, New Jersey, to her eventual destination,

MARCH/APRIL 2015

Sierra_Sue II.indd 13

Top: This early 1945 photo provides tangible evidence of the crude nature of the Sierra Sue nose art.

Thankfully the nose art was authentically recreated and not airbrushed and beautified.

Bottom: Dean W. Stitt, crewman of P-38, Border Belle, sits on the wing of Lt. Bob Bohna’s P-51 Mustang, Sierra Sue II on May 1, 1945. He was a member of the 402nd squadron and later transitioned into the P-51. Photo: via Doug Stitt.

13

3/17/15 2:55 PM

The dawn of a new era in the life of this combat veteran Mustang. Note the visible Alclad logos on the gear doors. Air Corps Aviation research revealed that these logos were visible when P-51s left the factory but quickly wore away. Photo: Bob Canepa

Advanced Landing Ground Y-32 Ophoven, near Zwartberg, Belgium. She arrived the first week of April 1945 and was assigned to the 402nd FS. After being hit on an armed reconnaissance mission, 1st Lt Bohna found himself in need of a new P-51 after he belly landed his first Mustang on April 8. He named his first aircraft Sierra Sue, so naturally the Mustang he was assigned on April 11 became Sierra Sue II, commonly referred to as simply Sierra Sue. Bob and Sierra Sue II flew some combat missions from Y-32 in early April 1945.

As the tactical fighter squadrons rapidly moved ahead with the advancing army, the 402nd moved to Y-99 on April 22 where it remained until the end of the war.

several years. In 1947, the Royal Swedish Air Force (RSAF) was looking for more Mustangs. The primary mission of the SAF before the war was bombing, but as the threat from Soviet Bloc countries developed, air defense with fighters became more important. After the war the Swedes updated their inventory with new, lowtime P-51s, including Sierra Sue II. If she hadn’t been a low-time fighter, she wouldn’t be with us today.

Sierra Sue II was transported by train to Ostersund, Sweden, in June 1948. There she was reassembled and brought up to airworthy standards. The reconditioning occurred at an airbase known simply as F-4.

From Sweden to South America The squadron stayed in Germany for quite a while after the war. Sierra Sue moved with the squadron to bases around Germany, including Sandhofen, Fritzlar, and eventually Furth near Nuremberg, where hundreds of surplus fighters, many brand new, were collected immediately after the war.

The new Mustangs, as well as the combat veterans, were stored at Furth Advanced Landing Ground R-28 for

14

Sierra_Sue II.indd 14

After the war, 44-63675 was acquired by the Swedish Air Force where it served with F-4 Wing at Osterund and F-8 near Stockholm. Note her USAAF markings are still visible.

Photo: Leif Hellstrom via John Dienst collection.

WARBIRD DIGEST #59

3/17/15 2:55 PM

Below: From 19541961, our subject Mustang served with the Nicaraguan Air Force. Its final assignment was as a gate guard at the Los Mercedes Officers Club. Photo: Tom Surlakvia via John Dienst collection.

In 1971, David Allender purchased and modified the Mustang with the intent of making an assault on Darryl Greenamyer’s 3Km World Speed Record. Fortunately those intentions did not pan out, otherwise she may not have survived to the present day. Sierra Sue returned to stock condition but still in the redorange Allender paint scheme. Photo: Dick Phillips

Warbird Recondition into Racer

It was common practice for the SAF to designate airfields by the wing based there. Thus, F-4 was also the name of the new fighter wing to which 44-63675 was assigned. It was named Gul Kalle (for yellow “K” in Swedish) and given the Swedish serial number 26152. In 1952, Sierra Sue II was shipped to F-8 near Stockholm, where she flew for two years as a proficiency aircraft and squadron hack.

In 1954, Nicaragua was in the market for Mustangs in order to expand and modernize their air force.

Consequently, Sweden was ready to transition into jets, so a transaction ensued. Sierra Sue II moved to Malmo, Sweden, was disassembled and transported to Managua, Nicaragua, where she served from 1954 to 1961. After service with the Fuerza Aérea de Nicaragua, 44-63675 served as a gate guard in front of the officers’ club at Los Mercedes. Most of the Nicaraguan Mustangs were purchased in 1963 by Will Martin and documented in his book “So I Bought an Air Force,” but 44-63675 wasn’t one of the 26 P-51s taken out of Nicaragua at that time.

MARCH/APRIL 2015

Sierra_Sue II.indd 15

In 1971, California-native David Allender purchased Sierra Sue II from Nicaragua, intending to make an assault on Darryl Greenamyer’s 3Km World Speed Record of 438.041 mph set in 1969. Once again, the aircraft was dismantled. With the help of Nicaraguan Air Force personnel, nine wooden crates were built to fit inside the cargo doors of a DC-6. The longer wing sections were airlifted separately to San Francisco while the rest of the aircraft was shipped to to Miami, Florida. Dave arrived in Miami a week later to pick up the parts. With the help of a friend, he loaded pieces of Sierra Sue into a rented Ryder truck and made the week-long trek across the country to Hayward, California, where she would be reconditioned into a racer.

Considering that Allender was more interested in his record-breaking mission than the Mustang’s combat history, he may not have even been aware that such a notable history existed. Interestingly enough, one of the young guys stripping paint off of Sierra Sue II before making speed modifications was very keen on the aircraft. Fortunately for later restorers, 18-year-old Lou DePropis took notes of the numbers he found. More amazing is that Lou kept those notes and they were extremely helpful in following the history and demonstrating the provenance of Sierra Sue II. Allender’s Mustang required extensive modifications in order to get her up to a speed of 500 mph at low altitude.

The wings were clipped at the factory joint and a foot was removed from the horizontal stabilizers. The angle

15

3/17/15 2:55 PM

From left to right: Eric Trueblood, Dan Matejcek, Erik Hokuf, Chad Hokuf, Doc Christgau, Mark Tisler, and John Christgau pose with Sierra Sue II before dissassembly for transport to the shop in Bemidji, MN.

1

of incidence of the wing was reduced and the wing leading edge was smoothed over with fiberglass to reduce drag.

Also, the Mustang was fitted with Hoerner wingtips, a cutdown canopy and turtle deck. Dave modified the plane’s Merlin engine to produce 3000 horsepower and made several flights in an effort to get the machine working reliably. Unfortunately, the aircraft failed to reach the racing potential Dave hoped for, thus no attempt was ever made on Greenamyer’s record.

3

Sierra Sue II Lives On In 1977, Dave sold the Mustang to Dr. Roger “Doc” Christgau, a Minneapolis area physician who served as a fighter pilot for the Air Force in Korea and Okinawa. He based his warplane at Flying Cloud Field in Eden Prairie, Minnesota.

When Doc repainted the plane to restore its original markings, he included Swedish artwork on the starboard side to represent his Swedish heritage and as a tribute to her service in the Swedish Air Force. For 34 years, Doc flew Sierra Sue regularly for recreation and at airshows.

Top: The Swedish yellow “K” and Gul Kalle markings. Middle: Mark Tisler and Chad Hokuf disassemble Sierra Sue II, preparing her for transport. Bottom: The fuselage lifted up from the wing.

Photos: Max Haynes, Courtesy of AirCorps Aviation.

In 2011, Paul Ehlen purchased the airplane from Doc Christgau, who was now retired and re-located to Austin, Minnesota. AirCorps Aviation organized a send-off event for the Austin community when residents learned Sierra Sue had been sold — they had grown fond of seeing Sierra Sue II in town and flying through the air. Doc told Paul that with a bit of tuning on the carburetor she could be flown right out. Consequently, Paul told Doc that Aircorps Aviation planned to disassemble the wing and fuselage and truck the Mustang up to Bemidji, Minnesota where the P-51 would undergo restoration from the ground up. Doc was heard to respond,” I’m the only one who ever wore out a P-51!”

16

Sierra_Sue II.indd 16

WARBIRD DIGEST #59

3/17/15 2:55 PM

1

Top: When Paul Ehlen purchased the Mustang, it came with two Merlins. One was overhauled by Roush Aviation for reliability and longevity and the second was built to period correct factory specifications for static display. Middle: Stripped engine compartment, Vertical Stabilizer and tail wheel assembly prior to restoration.

Photos: Courtesy of AirCorps Aviation Photo: Joanna Johnson, courtesy of AirCorps Aviation

MARCH/APRIL 2015

Sierra_Sue II.indd 17

Top: The gun bays are fully detailed with guns, feed chutes, ammunition, and placards. The only thing lacking is the smell of cordite.

Bottom: First engine run for Sierra Sue II. Photos: Courtesy of AirCorps Aviation

Preserving the history of one of the few surviving veteran combat warplanes and one of the most unmodified Mustangs in the world was important to the owner, so he entrusted the restoration to AirCorps Aviation, a relatively new restoration business. However, the company is owned by four men with extensive experience in restoration and maintenance. Erik Hokuf, manager, has accumulated 11 years of warbird restoration experience, while restoration manager, Mark Tisler, has a knowledge base that spans 25 years.

Fabrication manager, Dan Matejcek and Eric Trueblood, parts manager, have nine and seven years, respectively.

These men are no strangers to restoration projects as many were involved in the restoration of Aleutian Island Tiger, a Curtiss P-40K Warhawk that won EAA’s Grand Champion Award, plus Golden Wrench and Phoenix awards at Oshkosh in 2006. Also on their resumes is the combat veteran P-51D-20-NA Twilight Tear that won recognition as the 2011 Oshkosh Warbird Grand Champion.

17

3/17/15 2:55 PM

Restoration to Authenticity Begins In August of 2011, ground transport delivered Sierra Sue II to AirCorps Aviation and the long process of restoration began.

Early on, the owner and the restoration team decided to restore Sierra Sue II to her original beauty — the way she looked in Belgium after her nose art and lettering were applied. By that time fighters were no longer being completely painted. Incidentally, Sierra Sue II is bare metal, other than the wing paint that North American applied over the “aerodynamic smoothing material” to achieve a cleaner laminar flow. She wasn’t to be a polished, mirror-finished show plane. Today, there are some beautiful examples of almost mirror-finished P-51s in existence, but there were none in 1945. The rare aircraft was authenticated with mill-finished skins that included the inevitable scratches and dull areas caused by an acid wash used at the factory.

During disassembly, the AirCorps crew inspected every part of the aircraft and classified every single component into three categories: useable, in need of replacement and missing. As each part was removed, mechanics attached a color-coded zip tie denoting the coating used on the piece. Gray was used for bare metal, yellow for yellow zinc chromate and green for green zinc chromate, and so forth.

Provenance is important in a combat veteran because paperwork was sometimes sketchy when warbirds returned to the U.S. in the 50s, 60s, and 70s. There are always those who will dispute the real identity, so it was important to compare serialized parts to a list made up of observed serial and part numbers. The list was created through long hours of examination of NAA engineering drawings and developed into a spreadsheet.

Thus, parts were cross-referenced and checked to see if they were factory installed or installed later, contributed from another P-51 or replacement.

18

Sierra_Sue II.indd 18

WARBIRD DIGEST #59

3/17/15 2:55 PM

According to Erik, roughly 90% of Sierra Sue II below the skin remains original.

Even the grease pencil marks left inside the airframe by factory workers in 1944 were evident. In the case of a replaced part, an overlay was made of the original and used to duplicate it on the new piece.

Research showed that bare metal Mustangs rolled off the assembly line with the Alclad logo visible inside the airplane and on the outside skin in places. In service, the outside logos quickly wore off, but the restoration philosophy dictated that it should be there if AirCorps wanted Sierra Sue II to look like a factory-fresh Mustang. The modern logo was stripped from stock used for replacement skins and the 1944-era Alclad logo was reproduced and applied.

AirCorps found that wartime Mustang rivets varied in appearance because of slightly different anodizing from different suppliers. Some looked the color of natural aluminum, others had a yellow cast, and a few even were blue. The rivets are a big part of the factory-fresh look on bare metal surfaces so rivets were recreated to exact wartime specs by the National Rivet and Manufacturing of Waupun, Wisconsin. The various color rivets were put on randomly as they probably were when pulled from rivet bins on the production line.

References from 1945 indicate factory-fresh airframes were dull in areas where acid wash would have been used in spot welded areas. Additional details reproduced were cotton wrapped, lacquered wire, and more than 200 inspection marks, decals, stencils and placards. Sometimes the original fonts used were no longer available and had to be recreated. The engine in Sierra Sue II, was a low-time spare that was included in the deal with Doc Christgau.

This engine was rebuilt by Roush Aviation and received only minor modifications to increase longevity. The original Merlin engine was rebuilt without modifications to represent a historically accurate display example of a V-1650-7.

After more than three years of restoration, Sierra Sue II was ready to make her first-post restoration test flight on September 17, 2014. Doug Rozendaal flew up from Mason City, Iowa, to do the honors. During the flight Doug radioed data to AirCorps technicians who took notes, so they could make adjustments later. The test flight went well with only a recommendation to richen the idle and adjust the oil cooler door actuator to get the oil temperature where they wanted it. Doug said, “If this was a Sunday in late July we’d top her off and head to Oshkosh.”

A week after the test flight, the nose art was applied by Kevin “Max” Wisniewski, a retired firefighter who has a life-long passion for World War II history.

Ensuring complete authenticity, Max applied only original paint formulations that were available and used during the war, even though the result isn’t as durable as modern paint. Since wartime art was hand painted, Sierra Sue was to be hand-painted during her restoration, which presented a challenge. Most aircraft Sierra Sue II Restoration Photos: were never photographed in color during the war which makes it difficult for artists Joanna Johnson and AirCorps Aviation. to accurately reproduce nose art on combat veteran aircraft.

MARCH/APRIL 2015

Sierra_Sue II.indd 19

19

3/17/15 2:55 PM

Photo: Leo Correa Luna

Photo: Leo Correa Luna Photo: Leo Correa Luna

Photo: Leo Correa Luna

20

Sierra_Sue II.indd 20

WARBIRD DIGEST #59

3/17/15 2:56 PM

In researching the paint scheme, it was necessary to study period photographs closely, examine black and white shots, and then compare the hues to known colors from the Army Aircraft Color Standards reference book as well as interview 402nd FS veterans.

According to Max, “By photographing various color samples in black and white, I was able to paint on a scrap piece of aluminum. After comparing these pictures to the originals, we were able to determine with 99% certainty what colors were likely used.”

The AirCorps Aviation Team, left to right: (Front Row) Mike Dunn, Erik Hokuf, Brad Trask, Brian Bottolene; (Back Row) Randy Kraft, Chuck Cravens, Tina Moore, Ryan Underwood, Eric Meulebroeck, Dan Matejcek, Mark Tisler, Mark Robotti, Sam Walsh.

When Sierra Sue II was ready for her public debut, the team returned to Austin, Minnesota, where the whole restoration process began. It was a touching memorial to Roger “Doc” Christgau, organized by his brother, John and family.

Photo: Bob Canepa

The typestyle was designed to mimic the original blue script highlighted with red. In contrast to the beautifully applied lettering, the image of the pin-up girl sporting a cowboy hat painted to the left of the cockpit was crude in execution.

Max equated the painting to a style you might see on a carnival sideshow banner. Even so, it isn’t coincidental that “Sue” strongly resembles the lovely actress smiling from movie posters promoting the 1941 Gene Autry movie, “Sierra Sue”. It is possible the film’s attractive movie star, Fay McKenzie, inspired the portrait, despite its inelegant rendering. When Doc Christgau composed the previous paint scheme, he thought “Sue” was too ugly and chose to have a prettier girl painted on the fuselage. Regardless, historical accuracy dictated that the original less attractive appearance be duplicated. By virtue of undiluted attention to detail, Sierra Sue II captures a significant moment in American heritage and is recognized as one of the most complete authentic warbird overhauls in history.

Chuck Cravens, researcher and writer with Aircorps Aviation, chronicles a much more detailed and technical account of the history and restoration of Sierra Sue II in his book, “Combat Vet P-51, the History of Sierra Sue II, World War Two Survivor.”

AirCorps currently is working on restorations of a P-51C, a war veteran razorback P-47D and a Stearman N2S-1 flown by former President George H. W. Bush. More about those projects can be found at the AirCorps website and on facebook. http://www.projects.aircorpsaviation.com facebook.com/aircorpsaviation www.aircorpsaviation.com

MARCH/APRIL 2015

Sierra_Sue II.indd 21

Photo: Leo Correa Luna

21

3/17/15 2:56 PM