YEAR AROUND * I ECO OMYUTILIZATIONIF YOU WANT MORE ENJOYMENT FOR LESS COST

FLYA POWERED SAILPLANE

RF 5 B

TYPE SPAN L/D DELIVERY SEATS HP ENGINE MIN R/ S

SFS-31 49 ft 29 6 months Single 36 VW 2 .8 ft/sec

RF-5 46 ft 22 6 months Dual 68 VW 4 .6 ft/sec

RF-5B 57 ft 26 6 months Dual 68 VW/Frank 2 .8 ft/sec

Standard equipment includes : Airspeed indicator(s), Altimeter(s), Variometer(s), Mag-

netic compass, Gear warning light and horn, Safety harness(es), Seat cushion(s), Tai l

antenna, Cabin vent(s), Recording tachometer, Oil pressure gauge, Battery, Oil Temp .

gauge, Ammeter, Starter (elec .), Exhaust silencer(s).

S. Of7T-AV/AT/ON /NC.401 HOLMES OLVO. WOOSTEA, OH/O 44691 !2961 262-930 1

MOTORGLIDINGDonald P . Monroe, Editor

Vol . 3, No . 12

Published by The Soaring Society of America, Inc .

December 1973

Contents Page

EXPLORING THE SOUTHERN CALIFORNIA SHEAR LINE ,MOTORGLIDER STYLE, by Tasso Proppe 2

FOREIGN SCENE, by S . O . Jenko 4

ORYX, by Stan Hall 6

THE ECONOMY OF SELF-LAUNCHING SAILPLANES ,by Elmer Balint 7

A FEATHERING PROPELLER, by Dick Henderson 9

LETTERS 1 0

CLASSIFIED ADS 1 3

POSTFLIGHT NOTES 1 4

Cover :

Stan Hall's Oryx, by Michael Machat

MotorgZiding is published monthly by The Soaring Society of America, Inc ., whos eoffices are at 3200 Airport Avenue, Room 25, Santa Monica, California 90405 . Themailing address is Box 66071, Los Angeles, California 90066 . Subscription to Motor-gZiding is $5 .00 ($6 .00 outside of U .S .) for one year (12 issues), beginning wit hthe current issue .

Back issues are available at 50(p each .

Second-class postag epaid at Santa Monica, California . Reproduction of any of the material printed inMotorgliding, unless specifically excluded, is encouraged . Readers may wish to cor -respond directly with Harry N . Perl, Chairman, Powered Sailplane Committee, 390 7California Way, Livermore, California 95440 ; or Richard Schreder, Chairman, Air -worthiness and Certification Committee, Box 488, Bryan, Ohio 43506 .

ADVERTISING RATES, CONDITIONS, AND SIZE S

Display ads :

$15 for 4 page ; $25 for ½ page and $40 for full page . Prices are fo rfull-size, photo-ready copy . Extra charges for make-up, $3 .00 to $5 .00 ; reductions ,$2 .00 ; and photos, $2 .50 .

Sizes :

4-page, 3-3/8 x 4-5/8 ; ½-page, 7 x 4-5/8, o r3-3/8 x 9-1/2 ; full page, 7 x 9-1/2 .

Classified ads : 50 per line (40 characters )or portion thereof .

Circulation of the November 1973 issue was 820 .

EXPLORING THE SOUTHERN CALIFORNIA SHEARLINE, MOTORGLIDER STYLE

by Tasso Propp e

For the southern California soarin gcommunity, the shear line is somewhat o fa standard commodity, like ridge soaring .To me, it was new and I wanted to fin dout what it's all about .

The best explanation I could obtai nwas this : The shear line is a stationar yfront, a line along which two air masse sof different properties meet with an as -sociated exchange of energies ; in thi scase, it is the hot and dry desert ai rof the Californian hinterlands meetin gthe maritime air out of the greater Lo sAngeles basin . The latter air mass ishumid, not so hot, and smoggy . Sometimes ,you can really see the brownish soup sit -ting over the countryside . The exchangeof energy is heat transfer from the des -ert air to the cooler mass . Along th econtact line, the warmed-up cool air ex -pands and rises, being replaced by a con -stant flow from the cooler side of th efront . That means northwesterly windsand downdrafts inside the cooler air and ,of course, lift on the shear line itself .

This sounds all fine from excitin gverbal and written reports . However, theshear line isn't always that simple, an dmost of the time, it has a few deficien -cies . The rotor edge altitude is gen-erally limited by aninversion level, an dthe line is not continuous but broken upby the terrain of the hills underneath .Sometimes, though, when the air is un -stable, the rotor triggers thermals alon gits edge . They tell me that the shea rline itself can be recognized by a strin gof dust devils "you just have to fol -low . . . ." The lift is to be found alonga narrow edge, too narrow to circle in .the old urge to flip into a tight turnwhen you find lift leads you astray . Inthe shear line, you fly straight until

the lift quits, and then you try to zig-zag to where it might continue . However ,the lift line itself is crooked, and tha tmakes things more confusing .

I found the lift very moderate ,sometimes too weak form Crow to sustainaltitude . I also found out : If thelift is strong, it lasts only five t oseven seconds, and you better turn bac kand try to find that again : you have areal thermal by the tail that may affor dyou a better view from the top .

Since I don't have an unlimite damount of time at my disposal to wait fo rideal conditions,I have to make the bes tof what's there whenever I can afford t ofly .

On July 1, I took off from Hemet a t11 :05, heading west towards a quite vis -ible smog line . It was too early to ex -pect much soaring yet . I shut the en-gine down three times but the lift wa snot sufficient for my ship to maintai naltitude . So, I resorted to my "Adjust -able Gliding Angle" mode, keeping the en -gine running on minimum power so thatany presence of lift manifests itself a san altitude gain rather than a temporar yrelief from worrying about an emergencylanding .

It allows you to explore th econditions thoroughly and in comfort .

At 12:15, I hit a small area o fstrong lift which turned out to be a rea lthermal that carried me to an altitud eof 4900 feet, southwest of Sun City, goodenough for a straight-in glide into El -sinore for a (glider-) touch-and-(motor -glider-) go at 12 :47 .

From there, I needed the engine fo r15 minutes to climb out heading back t othe shear line-there was nobody aroun dto show me a good thermal .

At 13 :07, I located one, south o fSun City, cut the engine at 2600 fee tand soared to 6200 feet . With that al -titude, I glided back into the line o fsmog that started north of Sun City . Bythat time, there was enough lift in i t

2

to maintain an average of 3500 feet withthe engine off for good .

I traveled northeast, passing be-tween Perris and Hemet, hit another ther -mal at 14 :00 up to 5600 feet and bac kagain to shear line level which eventu-ally rose to 4200 feet northwest of Hemet .

By that time, I felt pretty smug-until disaster struck at 14 :30 . I noticeda dust devil moving slowly over the land-scape at a distance, and I decided t odive for it . Somehow, I didn't make it .When I arrived at where it was, I foun donly turbulence and no lift . I als ofound myself darn close to the ground a t1800 feet . (Hemet is 1500! )

Well, in a motorglider, this is notreally a disaster; you switch the igni-tion on and punch the starter button .After having soared continuously forl hr45 minutes, the engine needs a littl ewarm-up time before you demand climbin gpower for getting back up to where you

belong .The rest of the flight was unevent-

ful . I headed back to Hemet and cut th eengine eight minutes later at 3100 fee tin a thermal that got me up to 5600 feetwhere I joined the rest of the Heme tsoaring fleet that was cavorting aroun din an abundance of lift everywhere i nthat area .

The resulting logbook entry : I flewthe shear line in a low performance sail -plane on a day when nobody else coul dconnect to it .

Total flight time : 4 hr 25 min .Total engine time : 1 hr 34 min .

(35 .5% )Total expenditure : 84 cents . (2 gal

of automobile ethyl gasoline . My enginedoes not take to aviation gas too kindly)

The catch : ,I had to rely on seveninflight engine restarts,but that's wha tmotorgliders are meant for .

Photos by Ben Pesta

FOREIGN SCENE

by S . O . Jenko, Dipl . Ing . ETH-AMTECHSERVICES

The following summary is based onarticles in the August 1973 issue o fAviasport and the September 19 issue o fSkrzydlata Polska .

The first modern Polish auxiliary-powered sailplane SZD-45 Ogar began testflights at Bielsko-Biala . This new two-plane design features side-by-side seat-ing and a mixed construction : wings ,tail and forward section of fuselage ar efiberglass ; central part of fuselage an dboom are of aluminum alloy .

The engine is a VW Limbach SL-1700E Cwith a Hoffman 1 .5 m diameter propeller .

JET-POWERED SAILPLANEAn article in the May 1973 issue o f

the German magazine Flieger presents rea-sons for and a description of the Swis sauxiliary-powered sailplane Prometheus Iwhich has a jet engine . An abridgedtranslation of the article is presentedhere .

A few members of the Soaring Groupat the Swiss Federal Institute of Tech-nology (ETH) started in 1971 a designproject which would feature a jet engin einstallation in a high performance sail-plane . Some of the participants were :T. Bircher, one of the Diamant design-ers ; A . Schiller, the designer of FS-l ;P . Senn, experienced in aircraft repairwork, and D . Favarger, leaderof the tech -nical section of the Soaring Group .

T . Bircher received in December 197 0on a two-year loan from manufacturers aDiamant 18 and a jet engine "Eclaire II "(176 lb of thrust) . The original aim o fthe , group was to design a two-place per -forming sailplane with a jet engine (264lb of thrust) suitable for beginners aswell as experienced pilots ; also for wav esoaring and atmospheric research . Whil ethe advantages of a sailplane with anauxiliary reciprocating engine are wel lestablished the jet engine provides ad-ditional benefits such as flights at highaltitudes, less vibration, approximatelyfour times better power/weight ratio an dless air resistance . Furthermore, undercertain conditions the cost/hour for com-

Technical data: mercial

operation"pure" sailplane .

is

comparable

to a

Span 17 .5m 1 57 .4 ft) To facilitate the use

of the sameWing area 205 ft engine on various sailplanes

(i .e .,

re-Aspect ratio 16 movable installation) a soaring group ma yLength 26 .1 ft have, the

decision was made to positio nEmpty weight 1000 lb it above the fuselage .

Thus the jet en -Gross weight 1385 lb gine "Eclaire II"

was

installed on to pWing loading 7 .3 psf of the

Diamant 18

fuselage .

This wasMax . airspeed 124 mph not a new idea .

A substantial advantageRate of climb (power) 740 ft/min of the Diamant 18 were

the

wing

tanksGlide ratio (2 persons) 27 .5 which reduce the structural loads as com -Min . sink (2 persons) 3 .2 ft/sec pared

to a fuselage

tank installation .at 45 mph In addition,

the above-the-fuselage in-

4

stallation provides an undisturbed ai rintake resulting in a better performanc eand cooling as compared to an installa-tion in the fuselage .

The jet engine exhaust heats to someextent the fiberglass vertical tail . Analuminum covered vertical tail would b edesired but not required to facilitate aa better heat transfer (cooling) . On theother hand the response of the rudder isalso better . The nose-heavy moment dueto the jet engine thrust (above the cg )is partly compensated by the increase dair velocity due to jet exhaust over theunderside of the horizontal tail whichis mounted on top of the vertical tail .Flutter of the tail due to jet exhaust i sof no concern; however, it is noticeabl eat higher power settings (rpm) . All thes esmall problems caused by the T-tail coul dbe removed by a classical V-tail, prefer -able of metal construction .

The following technical data pro -vide an insight into this design modifi -cation .

The jet engine "Eclair II" develop s176 lb of thrust at 48,000 rpm, sea leve land 59° F . The total weight is 81 .5 lb .

Sailplane performance (jet engine no toperating) :

Gross weight (incl . 21gallons of fuel )

Stalling speedGlide rati oMin . sink

Sink at 93 mph

Sailplane performance with operating jetengine :

Theoretical ceiling

49,000 ftService ceiling

39,400 ftCruising speed

149 mphRange

186 miles

Altitude (km) 0

3

5 .5

8

10 12R/C (m/sec) 3 .7 2 .5 2 .0 1 .7 1 .1 . 8(@ 48,000 rpm )

Due to presently installed elec-tronic fuel metering device the sail-plane should be flown below 6 to 7 k m(22,000 ft) in order to avoid engineoverspeeding due to excess fuel supply .Thus the performance data above this al -titude are at present only theoretical .

1150 lb44 mph4 02 ft/sec

at 50 mph5 .25 ft/sec

5

cr.

CrewSpanWing AreaAspect rati oLengthEmpty weightGross WeightFuel capacityEnginePropeller speed reductionPropeller : wood, fixed pitchMain landing gear wheelsConstruction material-Douglas fir, fabri cWing construction-single spar, D-tub eAirfoil - NACA 63 3-618 - 632-615

STAN HALL'S ORYX

As was noted in October MotorgZidingStan Hall says that his two-place Oryyx

"is intended to be a poor man's RF-5B .Like the Cherokee II it isn't intendedto compete with anything except afflu-ence . It will be the Cherokee II of themotorgliding set . Nothing spectacularin the way of performance-but enough tohave a lot of fun with . And anybody wil lbe able to build it . All wood and fabric-just like the Cherokee ." Stan doesnot with to release construction details ,performance information, etc ., until theOryx is test-flown and debugged . Stan isincredibly busy and asks that reader snot write him forfurther details . Pleas erespect his wishes .

CONCERNING YOUR MOTORGLIDING SUBSCRIPTION

The number which appears after yourname on your address on the back cove r(or the envelope) represents the mont hof expiration of your subscription ; i .e . ,12 MG means that your subscription ex-pires with the December issue . Excep-tion : if there is no number, that mean sthat your subscription expires with th eJuly issue .

(The majority of subscrip-tions expire in July .) Renewal notice swill be sent each month to those whos esubscriptions are expiring, so it wil lnot be necessary for you to remember you rexpiration date .

THE ECONOMY OF SELF LAUNCHING SAILPLANE S

by Elmer Balint

Considering the high initial cos tof motorgliders many individuals an dclubs who are seriously interested i nthis type of machine are hesitant t omake the big move and place an order o fpurchase . Besides the capital investmen trequired, there is little informatio navailable regarding operating cost an dthe vague references to very low operat-ing cost are received with some skepti-cism .

The following is what we believe along-overdue, more-detailed account o fthe operating cost of motorgliders . De-pending on the type of ownership (indi-vidual, syndicate or club) and base o foperation, there are a number of vari-ables which we tried to reconcile . In

could be used as a framework, where in-dividual items could be substituted i flocal conditions warrant . We used ourown Sportavia-Puetzer RF-5B Sperber as abasis for our calculations . It should b enoted, that with the exception of th eCaproni A-21J, the Sperber is the mos texpensive motorglider on the market . Thefigures obtained are so much more aston-ishing . Lower priced models such as th eFaZke or the single seater Milan shoul dnecessarily show a corresponding reduc-tion of operating cost .

Now let us see how expensive thi s'Mercedes of the air' really is .

FIXED COST :

Depreciation (5% of $20,000) $1,00 0Insurance $

400Inspection for C . of A. $

10 0Total yearly fixed cost $1,500

any case, we feel that our calculations

OPERATING COST, ALL POWER FLYING :

Hours per year 100 20 0

Fixed cost/hr 15 .00 7 .5 0Engine cost/hr ($1200/1500 hr ) say 1 .00 1 .0 0Airframe maintenance 1 .00 1 .00Gasoline at 4 gal/hr 2 .00 2 .0 0Oil $ misc . maintenance 0 .25 0 .2 5Total cost/hr 19 .25 11 .7 5

Total cost/min 0 .32 0 .20

300

40 0

5 .00" 3 .7 5

1 .00

1 .0 0

1 .00

1 .00

2 .00

2 .0 0

0 .25

0 .2 5

9 .25

8 .0 0

0 .15

0 .13

7

OPERATING COST ALL SOARING FLIGHT :

Hours per year 100 200 300 400

Fixed cost 15 .00 7 .50 5 .00 3 .75Airframe maintenance 1 .00 1 .00 1 .00 1 .00Total cost/hr 16 .00 8 .50 6 .00 4 .75

Total cost/min 0 .27 0 .14 0 .10 0 .08

It is evident from the above, thatthe most significant drop in operatin gcost occurs at the 200 hour per yearutilization . Any variation of power onor soaring flight can easily be calcu -lated from the above figures to suit in -dividual users' requirements . Accordingto expected yearly hours to be flown ,clubs should be able to assess flyingfees to members and ensure a reasonabl eprofit for the club . Assuming 400 hoursper year we suggest $14 .00/hour or 24per minute of powered flight and $10 .00/hour or 17 per minute of soaring flight .This seems to be a reasonable price fo rthe average club member and comparesfavorable with the $12 .00 per hour aver-age for three years, which this write rpaid flying club-owned equipment .

However, this is not the whole pic -ture . Whether we realize it or not, th ecost of retrieve is substantial for the .cross-country pilot . Considering a simpl e100-mile flight, self-retrieve will cos t$14 .00, while trailering requires in thebest of the cases 200 miles driving at a-bout 12¢/mile . That is $24 .00 withoutcounting food and beerfor the retrievin gcrew . An additional fringe benefit i sthat the motorglider will be back on th efield within four hours and put to pro -fitable use in instructing for the res tof the day, while a pure glider is ou tof commission for the whole day, evenafter the shortest of cross-country fli -ghts .

A reasonably active soaring pilo twill fly approximately 100 hours per year .At this rate a motorglider seems to b ethe ideal solution for a four-pilot syn -dicate . Considering 25% powered opera -tion (self-launching and self-retrieve) ,the hourly cost for flying is $5 .00 whichis astonishingly low . Capital investment

would be approximately $5,000 .00 per pilo tif a Sperber is used, which, being a two-seater offers the dubious advantage o fyour mother-in-law coming along for th etrip . The single seater Milan would re-quire $3,750 .00 capital investment perpilot and even lower operating expenses .

Let us consider a private owner inthe $5,000 .00 class glider flying 100hours a season and doing ten 100-milecross-country flights .

FIXED COSTS :

Depreciation (5% of $5,000) $250Insurance $ 75Inspection for C . of A . $10 0Total fixed costs $425

OPERATING COST 100 HRS/YEAR FOR $5,00 0GLIDER :

Fixed cost $425 .00Airframe maintenance $100 .0033 Aero-tows (3 hrs . average

flight time) at $4 .00 per tow $132 .0010 retrieves 200 miles returntrip each 2000 miles at 12/mile 240 .00

Total cost

$897 .00

Cost per hour 8 .97

Cost per minute 0 .15

This compares with $5 .55/hr . or0 .09/min . for the Sperber operated by afour pilot syndicate . The same groupflying the single seater Milan could ex-pect 15% reduction of cost, which make sthe syndicate ownership of motorglider sa very attractive proposition . (Reprint -ed from June-July 1973 Free Flight . )

8

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**N**EDE*oN A LID

9

LETTERS

Editor :I would like to add to the inter-

esting account by Landon Cullum, Jr .which appeared in the July issue of yourmagazine .

Perhaps I should first declare myinterest in motorgliders . I am the Brit-ish agent for the Scheibe motorgliders ,and am thus in a better position thanyour reporter to have discovered manyother facts about the motorgliders be-cause of my knowledge and understandin gof German, and my familiarity with thes emotorglider competitions and meeting sdating back to 1965 .

(Concerning the scores) your re-porter has got confused between th edaily results and the cumulative scor eat the end of each day. For example itis impossible to score more than 100 0points on any individual day, but afte rthree days the scores of the leading mo-torgliders were over the 2000 mark . Th econtest was divided into single-seatersand two-seaters, and further divided be-tween advanced and less-advanced .

In the single-seater class they wer eall counted as advanced except the Schlei -cher Ka-8bM, which is the glider shownin the photograph on page 8 (of the Jul yissue) . Because there was only one i nthis category it was combined with th etwo seaters, and flew with the less-ad-vanced Scheibe SF-25 Falkes, the RF-5 ,and the experimental Mu-23 . Having arather better performance than these twoseaters it actually won this class . Ihave full details of this very interest-ing motorglider, which probably repre-sents about the cheapest way of having aself-launching single-seater, and woul dbe glad to make this the subject of an-other article for Motorgliding if you areinterested . Amongst the single-seaterswere also two Kraehe (not Kausch's asdescribed by your reporter) and regularreaders of Motorgliding will not need tobe told any more about them. They didnot take part in the competition .

The AK-1 is in fact fitted with thesame Hirth engine as is used in th eAS-K 14 and SF-27M's, but because it ismounted horizontally it looks quite dif-ferent to the SF-27M installation wher ethe cylinders are in the vertical plane .

A particularly interesting single-seateris the SF-27M fitted with Cirrus 18-meterfiberglass wings . This has been fitte dwith an experimental two-cylinder Hirthfrom a snowmobile and develops 44 hp . I tdrives through a cogged-belt reductio ngear . Another SF-27M had a similar en-gine driving the propeller directly . Inhis account of the visit to the Sportavi afactory atDahlemer Binz he gives the im-pression that the major parts of th eScheibe FaZke are built there . In fact ,the position is that the Scheibe FaZkeis in full production at the Scheib efactory at Dachau near Munich, but thatit is also license-built by the Sportaviapeople at their factory near Cologne .The SF-31 Milan is a marriage of th efuselage of an RF-4 with the wings of anSF-27M. Performance is not quite as goo das the AS-K 14, but many pilots prefe rto have an engine in the nose, and pre-fer the Volkswagen four-stroke to th eHirth two-stroke engine .

Developments in the motorglider worl dare now turning to increasingly high-per-formance aircraft . One pilot has alreadyordered a Schempp-Hirth Nimbus fittedwith a 55 hp Hirth retractable engine ,and a motorized version of the StandardCirrus was shown during the early day sof the competition in a semi-completedstate . It is also an open secret tha tthe Scheibe factory are studying the de-sign of a Bergfalke IV two-seater withretractable motor .

As this has a gliding angle of 1 in34 it should satisfy most people, eve nthough the performance will not reac hthe standards of the Caproni Calif (per-haps the price will be a little bit moreacceptable!) . The results sheet showsthe number of minutes of engine runningtime required by each competitor, and i tcan be seen that on some days almost al lthe gliders completed the course withoutusing the engine at all .

I have taken part in this competi-tion in previous years, and was luckyenough to be given a seat in a Scheib eSF-25C (that is the FaZke fitted withthe Limbach engine) on the first two com -petition days . The penalty for use o fengine is very severe in terms of los tpoints,. and it is worth circling for atleast a quarter of an hour instead of us-ing one minute of engine .

It requires

1 0

very fine judgment to decide when con-ditions are so bad that one minute o fengine will get you into better condi -tions and save more than 15 minutes o fcircling in a weak or dying thermal . Wehad several hours of soaring in clos ecompany with the Ka-8B, whose glider per -formance did not seem to be very muchbetter than ours, but which could fl yslower and more tightly in the very wea kthermal conditions prevailing .

Whilst thanking Mr . Cullum for hi skind remarks about the comparision be -tween the RF-5B and the SF-28 TandemFalke, I think it only fair to say tha tthe difference is very small indeed (i fit exists at all), and the poor result sof the RF-5B were largely due to one o ftheir top pilots failing to start hi smotor on the first day and having to land(this disqualified him for the day), andthe other pilot running into barograp hfailure which also disqualified him fora day . On a five-day contest one canno tafford to lose a whole day's points . TheSF-28 scores in being cheaper, and with -out a retractable undercarriage it i sless complicated and much less expensiv eif you forget to lower the undercarriage !As I am the Agent perhaps I should notpress my luck in this account by praisingthe product that I sell!

Peter Ros sBucks, Englan d

Open letter to Hans Zacher, who is theFather of the Burg Feuerstein motorglidermeet and a subscriber to this magazine .

Dear Hans :In the October issue of MotorgZid-

ing, I read S . O . Jenko's report on theMotorglider Meet, May-June at Burg Feuer-stein .

In the discussion, Mr . Jenko ex-plains the point formula and states thatany penalties pertaining to span, engin epower, and gliding angle have been drop -ped . I agree that there should be norestrictions to engineering perameters .However, I offer this as a vital inputto stimulate a sense of direction in mo -torglider design :

The real reason for motorgliders t ocome into existence is economy of opera-tion, to become independent of the cost -ly support systems of "pure" soaring

(winch, winch operator, power airplane ,tow pilot, line boys, retrieving crewand trailer) .

If somebody wants to perform excep-tional achievements (distance, altitude ,speed triangle), he should do so on to -day's or tomorrow's highly-bred fiber -glass or graphite composite ships . Thereis no immediate need to pursue the sam eline of development only with an engin ein it .

To make the joy of soaring access -ible to a broader spectrum of interestedpeople (we need a broader basis for th esport to survive), we must further th edevelopment of sailplanes that are mor eeconomical in terms of manpower usage and ,equipment cost . This means simplicity ofoperation and lower initial cost, bal -anced against soaring achievement capa -bilities .

Any point evaluation system, there -fore, should not only consider a pointdeduction for engine-on time (or fue lconsumption) but also, the accumulatedpoints from any task achievement shoul dbe divided by the cost of the machine (inkilo dollars, maybe) so that a motor-glider which cost only half as much ha sto fly only half the points to receiv ethe same recognition as the expensiveships in the evaluation .

A more sophisticated approach woul dbe to proportion the engine-on penalt yby a cost-of-acquisition factor so tha ta less expensive ship could afford moreengine-on time for equal opportunity . Ipersonally don't think much of this--al -though, in a real life environment, th eengine-on time of a motorglider seems t obe closer to 30% of flight time than th ewishful dream of 10% . This real life en -vironment may require some definition :it means flying when you happen to hav etime to fly between your job and the fam -ily projects . This does not normall yhappen to coincide with ideal soarin gconditions .

Dividingthe flown achievemerrtpoint sby the ship's initial cost would resul tin the following : Scheibe, Puetzer ,Schleicher, and whoever produces motor -gliders, will tend to design for moder -ate performance and, hence, less expen -sive gear . Stan Hall and the Brditschka sin Austria are already on that route .

There will be more people and club s

1 1

in a position to buy one and enjoy com -peting in meets . The new way of soaring-freed from the cumbersome ground sup -port--will become more known, motorglid -ing will be more visible and attract mor eprospective aeronauts . Once it becomesa recreation business like campers an ddune buggies, plastic and fiberglass mas sproduction will move in and make ' mcheaper yet .

Not until then can we afford to tur nto the expensive ships and let them loos ein unlimited competitions of their own .

So : Divide (by $) and conquer !

Tasso Propp eLemon Grove, Californi a

November 15, 197 3Editor :

Attached is a check to cover th enext twelve months subscription . I'mnot aware when my subscription expire sand want issues of Motorgiiding to cometo me . I'm enjoying them very much .

I first flew an RF-5B in England ,Biggin Hill, last Marchand again in Apri lwhere one was placed on order and re-ceived delivery of my machine in August .

Since obtaining delivery of the RF -5B, I have flown it -a total of about 10 0

hours .Accompanying me on several flight s

have been competition sailplane pilots ,military aerobatic instructors, amon gothers .

Comments from qualified people wit ha world of experience have been that th estalls have all of the characteristic sthat are highly desirable .

Behavior of the bird in every re-spect is good except takeoff . If thepilot permits the tail to come off theground prematurely, or applies power to oquickly-or worse, both-the machine wil ldart to the right like a jackrabbit . Ful lleft rudder must be employed for correc -tion . If takeoff is made tail down an dslowly applying power as prescribed i nthe manual, there's no difficulty .

Practical sink rate exceeds that o fthe book, (which is of course optimum) .I recently checked sink rate from 700 0feet to 1500. in still air and it clockedout at around 250 ft . per minute (ratherthan 195 as stated in the book) for tw opeople with full load, temperature ap -

proximately 40° F .A couple of my friends who are pur-

ist competition sailplane pilots lookedthe machine over and observed rather can -didly that they would like to have myservices this coming winter and spring ,to go up into the mountains and "snif ffor lift . "

Cross-country, ridge and wave soar -ing are this machine's finest character -istics . I believe that one can learnmore in a season of soaring, safely, withthis machine than they could in many yearsof experimentation with an ordinary sail -plane .

Time-consuming and laborious re-trieves are not my "cup of tea ." Neitherdo I enjoy the hassle with the farmerover crop damage, nor the specter of alaid up bird waiting for repairs .

Insofar as engine reliability isconcerned, the VW engine is tops . Atleast the VW will start with a great dea lmore reliability than any of the manyaircraft engines with which I've had s omany frustrating starting problems .

Certainly there are things to becriticized and this one is no exception .The turning radius could be shorter . Wewould all like to have a 50 to 1 glideratio with the sink rate of a buzzar dand the price of a Pinto automobile, bu tsuch is not within the realm of possi -bility . Better machines will be built ,but so far, the RF-5B appears to offe rthe best of both worlds, of soaring ,coupled with self-launching and reliabl erestarting capability .

George C . SellsJohnson City, Tennesse e

December 21, 197 3Editor :

. . .I am very happy with the ship .Now have fifty engine hours on it ; theonly difficulty so far has been with th epilot . I started it the other day at twodegrees below Fahrenheit with no problems .

The full feathering definitely im-proties sailplane characteristics and make sthe ship much more pleasant to fly . Neverhave any aggravation with windmillin gwith this Hoffman propeller .

George C . Sell sJohnson City, Tennesse e

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Editor :If we go back to August Motorgliding'

we might conclude that no one with apowered sailplane is interested enoug hin the request for thrust measurement sto bother to do anything about it andsubmit it . Thus it has been of interes tto research a little of the literature ,and what is better for that than Soaringmagazine?

Thus Isubmit some pearls from Harr yPert, in May-June 1955 Soaring .

The Nelson H-59 four-cylinder two -stroke cycle engine which develops 40 hpat 4200 rpm .

The mobile test stand which wasmade in order to establish some criteri afor design purposes .

The net thrust vs . rpm at variou sindicated airspeeds for a representativ etest propeller .

PDeopeC EyerNRos r re-sr 7--/-- fo7-E3r ,°Ro#. 4,3 ¢Z ROx-z4Se-.e- NO . rso 44/vEClone H-5-9 eW /vE04r_ aO°f D4.C' 4ess. 3a.iz%!y.

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40

zof'E'oPtccE* si°EEOrRf'M)

2000

3440

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Thanks for answering my request ,Harry, even if you didn't do it untiltwenty years before I asked for it .

Stephen du PontFairfield, Connecticut

CLASSIFIED AD S

DESIGNING & BUILDING your own aux -iliary-powered sailplane and in need o fsound engineering advice? For free de -tailed information send a self-addresse dstamped envelope to : Amtech Services-mg ,RD 8, Mansfield, Ohio 44904 .

TASSO'S CROW FOR SALE. Due to apossible European job assignment in May ,I have to find another owner . Price $3200.I will be around to help get set up . Fordetails, see March 1973 Motorgliding .Tasso Proppe, 1786 Eldora St ., Lemon

Grove, Calif . 92045 .

(714) 463-1570 .

WANTED : TWO-PLACE used motorglider .Hugh Currin, 2029 LeRoy St ., KlamathFalls, Oregon 97601 . (503) 884-9988 .

zoo '

/80

/G0

h

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Second Class Postage Pai dAt Santa Monica, Calif .

Motorglidin gc/o The Soaring Society of America, Inc .P .O . Box 6607 1Los Angeles, California 90066

la MG

POSTFLIGHT NOTE S

An article by Ron Moulton in th eDecember 6, 1973 Flight Internationa lreports on an electric motorglider . Moul-ton reports that on October 21, 1973 ,Heino Brditschka flew MD-El (Militky Br d-itschka Electric One) for 9 min 5 sec ,to an altitude of 300 m (975 ft), atLinz, Austria. Fred Militky, a Germanmodel designer, was attracted to the ex -Austrian Raab Kraehe (Crow), which isnow being produced by Heinz Brditschka ,Heino's father, as being suitable fo relectric drive . Brditschka provided th eHB-3 airframe . Moulton reports that aBosch 10-kW motor and Varta batterieswere used, with a belt-drive to a1 .5- mdiameter propeller . Thirteen horsepowe rwas produced, with a 132-lb gross weightincrease . Moulton states that with de -velopment, the prospect of 40-minut epower storage is feasible .

In the December 1973 issue of West-ern Aviation, Jim Wright, Hot VW's Edi-tor, writes about a development of a VW -based engine for homebuilts . Lloyd Payn-ter, 4032 Crown Point Drive, San Diego ,California 92109, a retired aircraft ma -chinist, relying on help from Joe All -dredge, of DMI Parts, of La Jolla, Cali -fornia, is aiming at a goal of 75-8 0horsepower from an engine weighing 150 -160 pounds . His engine is based on. aVW 40-hp crankcase . He uses a planetarygear reduction system, driven off theflywheel fiend ,of' the powerplant, which

gives a 30 percent reduction in rpm fromthe crankshaft, according to Wright . A68-inch propeller, with a 44-inch pitc his used . The engine is still in the pro -totype state . The displacement of thepresent engine is 1385 cc, but a 1600-c cengine is planned .

Meanwhile, the November 22, 197 3Flight International reports that Te dBarker, of Carlsbad, California, ha sbuilt a turbo-charged VW engine conver -sion which produces 105 horsepower wit h1834 cc displacement and a weight of 16 4pounds . It has dual ignition . A Rayjayturbocharger is used, and a Hegy 50 x 5 0inch. propeller turns at 3700 rpm . Thecost of a Barker conversion varies fro m$1-2000, according to Flight Interna-tional.

An article called "The Soaring Fli -ghtof Vultures," by C . J . Pennycuick ,,appearedw,in the December 1973 ScientificAmerican . Pennycuick describes some o fthe observations of vultures and othe rsoaring birds that he was able to mak eusing the unique capabilities of a power -ed sailplane . A Schleicher AS-K 14 ha dbeen provided by , Anglia Television an dOkapia Film for his research, which wa sconducted mainly over the Serengeti Na -tional .Park in Northern Tanzania an dneighboring areas of Tanzania and Kenya .

William Welch, of Danbury, Connect -icut, recently inquired about the where -abouts of motorgliders in this country ,with the hopes of using one in a studyof hawk migration .

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