LAMINAR FLOW WING
If you talk to enough aerodynamicists, you will probably get the opinion you’re after on the benefits of laminar flow from at least one of them.
Beech found no significant benefit at speeds flown by general aviation airplanes. The first Bonanza to fly (December 22, 1945) had a laminar flow wing. Beech shortly after flew a Model 35 with the old familiar NACA 23000 series airfoil and could detect no measurable difference in drag between the two. The NACA 23000 wing did, however, have better handling characteristics, so that was the airfoil selected. Ralph Harmon, who headed the Bonanza design team, would argue to his dying day that the Bonanza would have been about 6 knots faster had Beech gone with laminar flow … but he was overruled by their Chief of Aerodynamics, Jerry Gordon.
In 1961 we took yet another look at laminar flow on the experimental 0-35 Bonanza, with the same results. In 1963 we did introduce the Beech Musketeer with laminar flow. All Musketeers, Sierras, Sundowners, and Sports have it. It was purely a marketing “gimmick.” It did allow us to put the wing spar in a convenient location. The bonded honeycomb wing construction “might” help the laminar flow wing in cruise with less drag due to its smooth surface. If it did … it wasn’t measurable.
Comparing the Bonanza to any of the models in the Musketeer family, I found the narrow lift-drag “bucket” on the laminar flow wing to be a learning experience on approach and landing … you were either going too fast or too slow. Sure, you can learn how to handle it; but it didn’t have the gradual and predictable decay in speed on approach and flare of the NACA 23000 series wing.
RUBBER DONUT LANDING GEAR SHOCK ABSORBERS
Aside from the hobbyhorse ride on rough terrain, this method of absorbing landing loads has proven to be very good at Mooney weights. No air, fluids, or troublesome seals to be concerned about, and they last a long time. The Beech Musketeer series used the same rubber-in-compression shock absorber, with equally good results.
“PERKY TAIL”
At least that’s the way one woman described it in a letter to Mooney. Others have said the tail is on backwards. In truth, it is a variable incidence tailplane with the rudder swept forward. (The Lockheed JetStar also used a variable-incidence tailplane.) Al Mooney felt the swept forward rudder would remain effective in a stall long after an aft swept fin and rudder would lose effectiveness. Here again, talk with enough aerodynamicists, and you will probably find one that will agree with Al Mooney.
Ralph Harmon designed the M-22 Mooney Mustang with the same distinctive Mooney tail. All production units carried this tail, but Ralph did, later on, build and flight test an M-22 with an aft swept T-tail. It’s entirely possible that Ralph wasn’t convinced of the “perky tail’s” value. Much later, Roy LoPresti designed and flew the Mooney 301 with a conventional swept back tail of 50 degrees. He also used conventional trim tabs on the elevator and rudder. Although the M 301 was never produced, LoPresti must have felt there was no particular advantage in staying with Mooney’s trademark tail. Much later, in 1996, he told me that if he had it to do over he would have stayed with tradition and used the Mooney tail.
Probably the safest ground to stand on is to consider the Mooney tail a trademark … and leave it at that.
RAM AIR POWER BOOST
A big feature introduced on the 1964 M-20E Super 21 was called ram air or altitude power boost. This system simply consisted of an additional air inlet and a control lever to let induction system air directly into the engine intake. This feature allowed intake air to bypass the standard air filter. It was to be used only in clean air to avoid engine contamination and resulted in an increase in manifold pressure of 1” to V/z” for improved performance … and it worked!
We asked our engineers at Beech to provide us with the same feature, and they finally did— on the first 285 hp Baron models. Results were disappointing, and after a few years, the “ram air” configuration was dropped. We had experienced only a small differential in manifold pressure, plus there was always the risk of a pilot forgetting to go to the filtered air position on descent.
A few may remember that Al Mooney designed the prototype M-20 engine compartment to take a Continental 6-cylinder C-145-2H engine that developed 145 hp. Rachal and Hoffman wanted to use the 4-cylinder Lycoming 0-320 of 150 hp. (Several sources have indicated that this was because they were a Lycoming distributor in Midland.) They naturally prevailed over Al Mooney. Due to the need for quick certification, both cooling air and intake air were never optimized for the Lycoming. This may account for the benefit realized from the Mooney ram air power boost. The original standard filtered air system was designed for the Continental and was a poor fit for the Lycoming.
STEEL TUBE ROLL CAGE
Distinctively Mooney, it appears to some observers as a carryover from the progression from stick, fabric, and wire airplanes to stick, fabric and steel tube construction. The first 1500 Bonanzas had steel tube carry-thru structures for both the front and rear wing spars. All the Beech Model 18s had a center section carry-thru truss of welded steel tubes. This construction technique appeared on the first Mooney Mite and was carried over to the M-20 design; so it is, quite frankly, a vestige of early aircraft construction methods.
It has served its purpose, however, and has even been modified from time to time to improve, among other things, accessibility to instruments and radios. The steel roll cage has stood the test of time and even become a Mooney sales feature with regard to crashworthiness protection for Mooney occupants. Expect it to remain a “plus” feature rather than a liability. Under ordinary operational conditions, no excessive flight or landing loads are imposed on the roll cage, and in an accident … it has proven its value.
As with aluminum, signs of corrosion should be looked for by a qualified Mooney Service Center. The steel roll cage seems to be particularly susceptible to moisture trapped in various soundproofing materials used on certain models.
ENTRANCE STEP
Mooney has explored a full range of configurations on this feature. No step, fixed step, retractable step (from a hand crank in the cockpit), to a pneumatically retracted step (thanks to Dr. Karl Frudenfeld of “Positive Control” fame) which retracted on engine start-up and extended by use of springs after engine shut-down. The entrance step is now firmly fixed in place on current production Mooneys. It’s part of an optional group of items which are required if you want an airplane.
Why have a step? The Piper Comanche (depending on how much the struts were inflated), had an inboard wing trailing edge very close in height to that of a Mooney (only 1” to VI2” closer to the ground) and no entrance step. But the Comanche was designed with stepping on the flap in mind. The Mooney was not. Remember, the first models had fabric covered control surfaces, and the flap extension-retraction system was not designed with the idea of supporting the weights of pilots or passengers.
Mooney estimates the new streamlined fixed entrance step costs them about IV2 mph in cruise. Jerry Gordon, the aerodynamicist on the Bonanza design, estimated their retractable step was worth about 3 mph in cruise, but it was a longer step. In summary, retractable steps are bound to become a maintenance item sooner or later, and inconvenient for the ladies when they malfunction and refuse to come down.
CRUISE SPEEDS
The early Mooneys (pre-201) unquestionably gave more bang for the buck in terms of speed, but it was reported by many knowledgeable industry observers (and not a few owners) that both advertised and handbook speeds were often overstated. Among aircraft manufacturers during those years there existed an informal custom to guarantee performance within a plus or minus 3% of advertised. The performance was seldom, if ever, on the plus side. Several took advantage of this practice, but Mooney seemed to carry it to the extreme … “gild the lily,” so to speak.
One of the first things Republic Steel did after taking control of the company was to have the owner’s manual performance charts revised downward about 10%. They wanted to be able to guarantee performance numbers within some reasonable bracket. This change occurred almost immediately. Then, with the introduction of the Mooney 201 and all models that followed Mooney owners could be fairly certain that their airplane would achieve what the manual stated.
Even so, comparisons between Mooneys and other manufacturers’ products are sometimes difficult because the altitudes, weights, and cruise power settings considered to be normal by Mooney are often different from the industry norm. Having said all that, it should be enough to state that Mooneys carry four people faster and at lower cost than anything else on the market in their class … they always have.