Update June 3, 1997


Lars and Tom the day before the test flight.

The take off of the VmaxProbe was a wonderful sight to behold!  She climbed like she knew she belonged in the sky.  Lars continued to climb while he had good temps and power.  The 2SI motor was a strong a thunderous sound.  Lars radioed that the temperature was starting to climb, so he throttled back to let it stabilize and get a feel for the controls.  Everything was going as planned.  He had a chase plane go up after him.  They radioed that "that thing is FAST".

After about 5 minutes of successful flying, Lars decided to bring her in.  It was a picture perfect approach.  About 1000 feet down the runway, he was holding her off at about 5 feet.  Then something went wrong.  The aircraft dropped abruptly, the left wingtip struck the ground and the aircraft rolled and struck the runway inverted.

Geneva and Tom were the first ones at the scene.  Lars sustained a traumatic head injury and passed away at the hospital 6 hours later.  He appreciated all the support you have given him and it was your support that helped make his dream possible.

This is the article that appeared in the Houston Chronicle. 

9:20 PM 6/8/1997

Aviator killed in crash is remembered for his love of speed


Copyright 1997 Houston Chronicle

Above his computer, Lars Giertz posted a sign that summed up the abiding passion in his life. "Fast, Faster, Fastest," it said.

A man in love with speed, Giertz wanted to design and build the fastest experimental plane of its kind in the world.

He wanted it so bad it may have killed him. He died June 1 after the plane crashed at a Brazoria County airport.

When he is eulogized today at Salem Evangelical Lutheran Church in Houston, the Sugar Land resident likely will be remembered for many things -- how he came to the United States in the early 1950s from Sweden to attend SMU on an engineering scholarship; how he quit school to join the U.S. Army as a shortcut to American citizenship; how he was so rabidly pro-American he refused to allow his children to be taught Swedish.

More than anything, though, his quest for speed was a central theme in his life.

As a young man, he raced club cars against Carroll Shelby and Dan Gurney, men who later earned fame as race car drivers.

Then, in the late 1970s, he received his pilot's license, and his fascination with airborne speed began.

During the last two years, Giertz's attention became focused on a futuristic-looking experimental plane he had spent more than 5,000 hours building. He christened it with a name that seemed to come from the pages of science fiction -- the VmaxPROBE. Giertz declared it to be "an outrageous new aircraft," and it impressed everyone who saw it, from commercial airline pilots to NASA engineers.

"It looks like a toy in a picture, but it was way ahead of its time," Dave Mudge, a pilot for U.S. Airways, said of the aircraft. "He had something really special."

Mudge and others were convinced the aircraft would smash a dozen aviation speed records for experimental aircraft in its weight class.

Built of lightweight carbon fiber, the aircraft was only 14 feet long. With a push propeller located at the rear of the plane to enhance speed, the aircraft's wing design had been generated from NASA to reduce the amount of drag the air exerted as the plane flew.

In layman's terms, there was virtually nothing on the aircraft in the form of wrinkles, joints or rivet heads to slow it down.

"His whole airplane was built perfect," said Mudge, 37, who lives outside Charlotte, N.C. "He was on his way to building a machine the world would take notice of."

Giertz, who had worked as a television producer in Dallas and later started his own film production company in Houston before launching his own airplane-building business in 1987, believed the VmaxPROBE could fly more than 300 mph, well beyond the 213 mph world record for planes in the 300 kilogram weight class. The consultants who worked with him agreed, but not everyone shared Giertz's enthusiasm.

Jim Szabo, an out-of-work computer technician who volunteered to help with sanding work on the plane after meeting Giertz through the Internet, said Giertz was so obsessed with the experimental aircraft that he reminded him of a "mad scientist."

"He had an ego twice as big as his hangar," said Szabo, 52, who left the project after three days. "I didn't care for the work environment."

Giertz's family says Szabo never really knew the man he's criticizing, but they concede the family patriarch was intensely competitive.

By example, they recall his decision in 1974 to break the world endurance record for radio-controlled model airplane flying -- a milestone held at the time by a Japanese man.

So pro-American that it bothered him a foreigner held the record, he resolved to set a new mark, and did so by flying a radio-controlled aircraft for 14 straight hours.

To do so, he had to redesign the model airplane, said his sons Tom, 35, and Riley, 38.

"To him, the fun part was designing it and building it," said Tom, who worked with his father in the family aviation business.

The love of improving the design of something apparently ran in the family. Giertz's great-grandfather, whom he was named after, was Lars Magnus Ericsson, the so-called "Alexander Graham Bell of Europe," who designed the modern telephone handset and began the Ericsson telecommunications company that thrives today.

Giertz's 92-year-old father, Bo, was well known in his own right, too, as a retired archbishop of the state-sponsored Lutheran Church in Sweden, where he became a public figure because of his conservative views.

Despite setbacks, which included trashing the first experimental airplane he designed and built, the bishop's son seemed poised to make his own mark on the world as the VmaxPROBE began to take shape this year.

Before the plane was flown, Giertz unveiled it at a February barbecue he staged for 150 people, including some NASA engineers.

In April, he hauled it to Lakeland, Fla., to show it off at a gathering of experimental airplane buffs, where it was the biggest hit of the Sun 'N Fun air show.

The plane also had garnered some media attention with an article in Sport Aviation, a magazine for members of the Experimental Aircraft Association.

Giertz did not toil in anonymity.

While building the plane, he kept thousands of aviation enthusiasts apprised of his progress through a web page he maintained on the Internet at www.hal-pc.org/~giertz/.

His Internet journal elicited messages from a worldwide audience, and he filed regular dispatches on his progress. In his May 31 dispatch, Giertz announced all was ready.

"I have therefore decided to attempt the first test flight for tomorrow around 8 a.m. at the airport," he wrote. "I will report the results when I return home on Sunday p.m."

For the test flight, he had taken the plane to the Brazoria County Airport because its north-south runway lessened the chances of crosswinds posing problems.

Before taking off, Giertz had requested that the airport's only emergency worker on duty that morning be on standby, recalled interim airport manager Sharon Craig.

Choosing not to wear a helmet, Giertz crammed his 6-foot-4 frame into the tiny airplane and the VmaxPROBE took off without a hitch.

"That thing is FAST!" a pilot in a chase plane radioed to the ground.

After five minutes, though, Giertz reported the engine temperature was starting to climb, so he decided to land.

His approach was fine, but about 1,000 feet down the runway, as Giertz was holding the aircraft about five feet off the ground, the plane suddenly dropped.

The left wing tip struck the ground and the aircraft rolled and landed upside down.

Giertz, pulled from the plane by his son Tom, died six hours later at a Galveston hospital from head injuries. He was 63.

The plane, though inverted on the runway, did not catch fire and remained intact, surprising the Federal Aviation Administration investigator who arrived at the scene.

As word of the crash spread, e-mail messages of condolence began pouring in from hundreds of people who had tracked the progress of the VmaxPROBE project on the Internet. "Australia, Austria, Germany," said Giertz's son Tom. "His web page had been getting about 80 hits a day from people all over the world."

The younger Giertz assured everyone that his father had accomplished his goals even though his test flight had ended in tragedy.

"My father's dream was to build and design the world's lowest drag man-carrying aircraft. That was truly his dream and he did live that," he said.


Lars and Tom making final checks for the test flight

an outrageous new aircraft for FAI world record attempts

No, it is not a model, it is the real thing as it rolled out on Feb 2.


The VmaxPROBE was designed to be the ultimate low-drag, manned, piston-engine powered aircraft. It was built in Houston, Texas by the designer, Lars Giertz. After initial flight testing, scheduled for late April, attempts will be made to establish several new FAI world records in the 300 kg and 500 kg classes. This web document is is intended to inform and entertain you as I share the trials of the project.



Wing span: 14 feet
Chord: 2 feet
Wing area (exposed): 24 square feet
Length:14.5 feet
Fuselage cross-section: 30.5 x 23.5 inches (oval)
Dry weight : 410 lb.
Total wetted area: 139 square feet
Flat plate equivalent (calculated): <.45 square feet
Engine: AMW 808cc, 3-cylinder in-line, two stroke, liquid cooled, 100 HP



Design philosophy.

The sign above my computer says:

Fast, Faster, Fastest

Alex Strojnik, whose books inspired me to start this project in the first place, has convincingly demonstrated that a pusher configuration is necessary for ultimate drag reduction. Why? Well, in order to go, say, 200 mph in a tractor engined aircraft, the air stream along the fuselage will have to go 220 mph. That adds up to over 20% increase in skin drag. Add to that the horribly dirty front-end, the disturbed and turbulent airflow over the fuselage, and you are wasting a very significant part of the available thrust.

But pushers have their own dirty little secrets. Their major drawback is that the airframe disturbs the air before it reaches the propeller. This causes the prop to go into all sorts of undulations that wastes power and can lead to catastrophic failure. Have you ever noticed that all the Rutan style canards have unique slapping prop noise? Well, that is the sound of the prop fighting with the dirty air from the engine cowling behind the aircraft.

The only props that can be used on pushers for any extended period of time are made of wood. Many attempts have been made to run various composite and metal props. They all seem to fail eventually. A few custom made composite props have shown promise, but none of the currently advertised props have worked out.

So we run a fixed pitch wood prop.

There are ways to limit the amount of turbulence in the air entering the pusher prop disk. NASA's research on cruise missiles and RPV's shows that the trick is to increase the distance between the flying surfaces in front of the prop to one chord length. This gives the disturbed air a little more distance to calm down before it hits the prop. A slim fuselage in front of the prop helps a lot too.

The bottom line is that a well-designed pusher airframe requires less thrust than a tractor configuration.

My thanks go to the pioneers Molt Taylor, Ed Lesher and Alex Strojnik. The air is less disturbed behind them!


There is a VmaxPROBE in the Houston City Dump!

After two years of steady construction of the first VmaxPROBE, I proudly had it on the gear. It was a pretty neat airplane. I had designed and built a fully retractable tri-cycle gear that was really nice. The only problem was that the gear doors represented about 60% of the bottom of the wing, and the majority of the bottom nose. So much for laminar flow along the fuselage and under the wing. I also had built separate flaps that I did not need, and there was no provision for re-flexing the wing section to fine tune the lift at high speed. I should have stopped reading after I started the construction!

I also became disenchanted with some of my composite work. It was too heavy. It was fiberglass. The wing section was all wrong. So I let the airplane collect dust for two years.

Then one day I took deep breath, saved the useable pieces and then threw the rest of the first VmaxPROBE in the dumpster.

Another two years went by before I had the time and money to start the new version I am building now.


What'll she do??

The top speed (Vmax) of any aircraft depends on two factors: available thrust and flat plate equivalent (drag). It is a simple formula: Speed=((146625 * Propeller Efficiency*Horsepower)/Drag)^.333. The VmaxPROBE's flat plate equivalent(drag) has been very carefully calculated by NASA aerodynamiscist (ret.) Bruce Carmichael, my tireless consultant who keeps me on track. He estimates a drag range of between .34 (optimum laminar flow across nose and flying surfaces and no aerodynamic surprises) to .60 (fully turbulent and no laminar flow). Plugging in numbers of 100 HP, 85% prop efficiency and an FPE of .45 we get 301 mph.

The current 3 km record in the 300 kg FAI class is 213 mph, and in the 500 kg class the record is 277 mph, and the Nemesis should soon have official FAI certification on the 285mph run at OSH.

Although I did not design the VmaxPROBE for the time-to-climb FAI record classification, Bruce has calculated that with 120hp the theoretical 0-3000 m climb could be run in two minutes and 40 seconds and the 0-6000 m in five minutes and 40 seconds.

The fuel capacity is about 26 gallons (24 in the wings, 2 in a header tank). With a fuel burn of 30 lb./hr, which would produce 50 hp, the aircraft would cruise about 240 mph, assuming a .45 FPE. This would allow over five hours of flight.

All of these numbers are of course only mathematical projections at this time.

Outrageous isn't it.



The entire airframe is constructed of graphite fibers and various epoxies. There is also some Nomex honeycomb, and I cored the bulkheads with high-density Klegicell. The wing and fuselage skins have a .250" light foam core in strategic places. The windshield is .125" plexiglass. The landing gear is .500" 2024-T3, and it's main attach points are reinforced with C-grain Douglas fir. The driveshaft is a beefed up version of Martin Hollmann's Nova design. The first testing prop has been carved by Fred Felix, and he just delivered a high pitch prop for all-out performance runs.

Here are some sample weights of parts as things were built:

  • The outer fuselage skin (two layers of 5.7 oz graphite cloth) weighed 13 lb.
  • The finished fuselage (less metal parts and paint) 80 lb.
  • The four wing skins came in at 3 lb. each, the two main spars were 6 lb. each. The two unpainted wings totalled 48 lb.
  • The weight of the painted aircraft, less metal, came out at 182 lbs.
  • The gear, with Matco 4" wheels, brakes and tires weighs 24 lb.


My engine criteria in designing the VmaxPROBE were simple. I wanted maximum power from minimum weight and size. It should be liquid cooled for minimum cooling drag.

The AMW 808cc, three cylinder in-line two-stroke is perfect. AMW engines are modular in design, and can be had in in-line two cylinder versions, in-line three, opposed four and coming soon, a new version of the opposed six. Various versions of AMW's have spent over ten years on the SCCA racing circuit, run power plants high in the Andes, and are currently powering many ultralight and larger experimental aircraft. My version has fuel injection, and of course, a built-in quick-change gearbox. There is a full electrical system, including generator, starter, water pump and solid state ignition made by ElectroAir (Jeff Rose's superb, programmable system that recently was instrumental in setting the FIA C1A altitude record). It weighs 125 lb. dry. Add 10 lb. for the Griffin aluminum radiator, hoses and coolant.


Current status.

I started on the new VmaxPROBE in early May,1995. On February 2, 1997 I invited the local EAA'ers to come out for a BBQ and see the roll-out of the VmaxProbe. The weather was great, and over 150 airplane nuts showed up.

I had finished the paint job, and it looks really great. The base color is silver and the rest is metallic lapis blue and red with a slight metal flake. All the paint is acrylic laquer, and it polished out to a superb finish. The finish and paint took about 1000 hours. Yuk!!!

So far I have about 5000 hours in the project.

Orion GPS, developers of the FAI accepted GPS data logger, has supplied a GPS data acquisition recorder to document upcoming record attempts.

By Sunday, March 9, I had completed the initial engine test runs in the airframe. There were no noticeable vibrations in the drive train up to 6000 engine RPM ( the maximum obtainable in static position with the first test prop from Fred Felix). The engine is EXTREMELY LOUD, since there is no muffler or tuned exhaust system. The fuselage aft of the exhaust pipe has taken a pretty good scorching.

I put an electronic scale in front of the aircraft, ran the engine full tilt, and got a static thrust reading of 185 lb. The engine monitoring module could not stand the airframe vibrations, and had to be isolated with a foam base. It still goes crazy, and I will have to install a separate on-off switch to keep it running.

I then did some slow-speed (say up to about 40 mph) taxi tests. During the approximately two mile taxi test, the engine did not display any overheating symptoms. The aircraft is a little slow to turn below about ten mph, but above that it acts just like any other tail-dragger. The fixed tail wheel works well. I also ground off the bottom of the lower vertical stabilizer and tail to fit the required ground clearance.

I have received the new engine mods, and it is installed in the aircraft.

To my chagrin I discovered some small holes in the wing tanks, so that has to be fixed before I fly. There have been other minor snags ( isn't there always?) so there will be no testing until after Sun-n-Fun.

The week at Sun-n-Fun was great! Crew chief Tom Giertz and I towed the VmaxProbe down to Lakeland on Thursday before, and spent a marvelous week visiting with the thousands that stopped by to see little thing. It seems EVERYBODY stopped by. Thanks again for your support!

As of April 24, I have done the following "last minute" stuff.

I had ordered a special 2 1/4" air speed indicator from UMA that was marked for the anticipated speeds of the VmaxProbe. I took the aircraft to my favorite A&P for a calibration check. If I had not done that, I probably would not have survived the first test flight. The unit was grossly out of calibration. If I had believed the markings, I would have stalled on final. At my anticipated approach at Vs times 1.3 (105 knots) the true airspeed was actually 80 knots... well below stall. So, again, be careful guys, there is rotten stuff out there, and don't assume that everything you buy is good and safe. I have come to believe that EVERYTHING that is non-certified is dangerous to your life.

Got the Terra navcom wired, and it works well. Still waiting for the transponder. The Terra people at Sun-n-Fun gave me vague excuses why deliveries are behind.

US Airways captain Dave Mudge, who brought a gorgeous BD5 to Sun-n-Fun offered to let me fly his plane before I took mine up. Last Monday I flew to Charlotte and had a deligthful couple of days with Dave Mudge and his family. The BD-5 was surprisingly docile, and I had no difficulty flying it...even landed it on first try. Thanks, Dave!

So, I say again, as I have said for the last six months: We'll fly in another two weeks.

May 14...

Didn't like some slop in my aileron linkage. I had used several u-joints in the circuit, and they just didn't cut it. So, I ripped out all the linkage, redesigned it, and rebuilt it. It is much better now, but of course I had to tear out a bunch of fiber glass to redo it. Tonight I finally got all that glasses back in.

The CG now is excellent (24-25%), as suggest by Bruce Carmichael and David Lednicer after much analysis of the airframe.

An interesting footnote: David Lednicer, after doing one of those fancy wireframes of the VmaxProbe, determined that the total wetted area is 139.9 square feet which he says is the smallest man carrying aircraft ever built.

May 15...

Had Jordan Propeller, a local outfit with mobile facilities, come out and have a look at the drive shaft/prop, After some fiddling, they determined that the propeller/shaft combination was extremely smooth... they measured a .30 vibration, which is well withing acceptable parameters for certified spam cans. So it looks like the engine/shaft/prop propulsion train might work out fine.

Re-ran the engine under 84 degree, high humidity conditions. Changing from basically standard conditions which gave 185 lbs of thrust at 5800 rpm, I now got 150 lbs and only 4600 rpm. Clipped one inch off each prop tip, and that got back the rpm. Didn't have time to check the static thrust. The engine in not running right. It now bogs down after a few seconds of wide open running. I have a meter connected to the timing output of the electronic ignition unit, but deviating from the recommeded factory timing setting does not help. I'm trying to find a cute way to determine whether it is fuel or ignition. I sure can't fly until the thing runs like clockwork...

This stuff can sure be frustrating.

May 17...

Made a fuel flow check and discovered that the mechanical fuel pump only put out 7 gph. Called 2SI and found out that one of their engine people had given me wrong info on hose connections... I was feeding the engine with the return flow! So I pulled the engine out again and plumbed things correctly. The factory has promised to send me an engine manual.

Now it runs fine. Tomorrrow AM I will make a final medium speed taxi test at Houston Southwest Airport and then move flight testing to Brazoria County Municipal in Angleton, TX where 7000' and good runway direction is available.

May 20...

Taxied another four lengths of the runway. The aircraft is a little twitchy, tries to steer to the right, but I got it up to over 50 mph without running off the runway. Discovered that a one inch by six inch piece of one of the prop blades was missing. Apparently a major rock took it out. Fixed the prop with new wood and some carbon fiber cloth. Also did an alignment check on the main gear. Sure enough, the right main was toed out about 1.5 degrees. Shimmed the axle .040 to correct the tracking error. No wonder the rascal was squirrely...

Pulled the engine and wings and loaded the aircraft in the trailer. Tomorrow I'll haul it down to Brazoria County Municipal and reassemble it in a hangar I rented for a month.

May 22...

Finally got the aircraft to the new airport and re-assembled it this afternoon. The weather is gross, and the forecast is for more rain and yuk for the at least the next two days. If I get a decent window, I'll do a little more taxiing.

May 29...

I have now done several taxi-runs at Brazoria County Airport (LBX). The aircraft handles very well at high speeds, and rudder control is positive from about 50mph. Tomorrow the aircraft will get a final, thorough tech inspection by my crew and outside fresh eyes. Then I'll do one more taxi to look at elevator control and aileron sensitivity.

If that works, I may blast off this week-end, weather permitting.

Sat AM, May 31...

Yesterday (Friday, May 30) I made another high speed run with ten gallons of fuel in the wings, and could find no reason to do it again before attempting a test flight. At 50 mph the ailerons are becoming very powerful. I ran another CG check. I am at 25.25%, which is exactly nominal.

A major line of thunderstorms roared through here around 2AM this morning, and now residual heavy clouds obscure the morning sun. There is, however, a strong push of northerly air behind it, and by tomorrow morning (Sunday, June 1) the temperature is forecast to be 62 degrees with associated low humidity. I have therefore decided to attempt the first test flight for tomorrow around 8AM at the airport.

I will report the results when I return home on Sunday PM.

Many, many people have written in from all over the world. Your encouraging words and incisive questions have helped make this webpage and the project worthwile. Please keep writing. The first thing I do when I get home at night is look to see if there are any messages on the computer. It is a joy to connect with people of the same interest.

Your comments, please?

susan @ rensmaas.eu

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