How many new things can a new design have ?

Discussion in 'Hangar Flying' started by topspeed100, Feb 2, 2011.

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  1. Feb 2, 2011 #1

    topspeed100

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    I found this LF 2100 article today; Popular Science - Google-kirjat

    Very serene design. Something did go wrong since it never became the next big thing.

    Was it those two engines in fuse / one fan unit...( dangerous/risk ? )...Y-tail...materials used ?
     
  2. Feb 2, 2011 #2

    orion

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    Are you referring to the Lear Fan? If so, that's a fairly long story. Nice looking design but relatively poor execution. The plane functioned well so no, the engine configuration was fine, as was the tail. The bottom line though was that it was built of composites but the structural configuration was identical (literarily) to that of a metal assembly. Bottom line: Failed to get certification for pressurized operation and by that time the company had too much invested and could not fix the problems.
     
  3. Feb 2, 2011 #3

    topspeed100

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    Yes Lear Fan 2100 a design originated by the late Bill Lear of the Lear Jet Corporation.
     
  4. Feb 3, 2011 #4

    autoreply

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    If I recall correctly, they also had major gearbox problems:
    http://www.flightglobal.com/pdfarchive/view/1985/1985 - 1874.html

    I'd still love to see something alike, but then with a counter-rotating prop and a well executed structural design. If the inner shaft is designed to be contained, even when an explosion of the shaft happens, you could have true independent engines/props on the same axis.
     
  5. Feb 3, 2011 #5

    topspeed100

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    LF 2100 was inspired by the oil crisis of the 70ties.

    IT GOT A MILEAGE PER PASSENGER SIMILAR TO dHdRAGON rAPIDE, BUT WAS ABLE TO FLY JET SPEEDS.

    ( Sorry caps lock on )

    Remarkable machine in any case..and it flew unlike Planet Satellite.

    http://en.wikipedia.org/wiki/Planet_Satellite
     
  6. Feb 3, 2011 #6

    TFF

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    I believe one of the other problems with it was noise. With noise restrictions coming it was a loud airplane. You dont see many Lear 23-25s any more because of that.
     
  7. Feb 3, 2011 #7

    Lucrum

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    I may be wrong as it was a long time ago but at the time seems like I heard that the FAA's relative inexperience with certifying composites may have played a role in the planes demise as well.
     
  8. Feb 3, 2011 #8

    orion

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    Actually, noise is where the LearFan excelled in that it was substantially quieter than the jets of the day. The gear box issue was subsequently solved several years after the program's failure as Soloy developed a similar product.
     
  9. Feb 3, 2011 #9

    topspeed100

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    I have spoken ( in the net at aafo ) or rather been in the same thread with a pilot who test flew it...he says the plane had strange structural bang heard once...and several times the dirty air entering the prop caused some vibrations or some similar trouble...maybe just odd sound. I am not 100% sure..since the thread must be 5 years old by now.
     
  10. Feb 3, 2011 #10

    TFF

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  11. Feb 3, 2011 #11

    Topaz

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    Odd sound is certainly possible - and pilots notoriously don't like anything that sounds different, amongst other things - but my recollection is the same as Orion's: the airplane was supposedly very quiet.

    The Piaggio P-180 Avanti II is a relatively quiet airplane, but it also has a very unique sound, due to the five-bladed props operating in the wake of the wing. There's one that flies into SNA about once a day, and I always know when it's flying overhead on approach. The sound, while soft, is that distinct.
     
  12. Feb 4, 2011 #12

    topspeed100

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    The story by test pilot;

    For those interested, I will try to add some clarification to the "E" number/"N" number history of the LearFan program.

    E-001/N626BL:
    First flight was on 12/"32"/1980. Contract commitment to the British government for continued funding was to fly on or before 12/31/1980. It was an "act" by parlaiment to declare that day as 12/32/1980 as they obviously felt that we had fulfilled the spirit and intent of the contract.

    The first takeoff was made by Hank Beaird in the left seat with test pilot Dennis Newton in the right seat. The first landing was made by Dennis Newton in the left seat with Hank in the right seat. Don't even ask..........

    My first flight in E-001 was on 7/21/1982 with Hank as my instructor. E-001's last flight was 7/20/1983. Mark Gamache was with me and we were accomplishing hydraulic system heating tests at FL250. We experienced an explosive decompression, declared an emergency, descended very carefully and landed straight-in on RW26. Two days prior, a combined pressurization/bending/torsion ultimate load static test ended in an explosive decompression due to collapse of the lower aft pressure bulkhead of the static test article. That failure was on our minds during the emergency return to Stead. Maintenance could find nothing wrong with E-001 over a three day examination, but the plane was grouded, parked in LearFan's back lot and was relagated to becoming a garbage can for discarded carbon-fiber parts. E-001 still hangs in the Museum of Flight at Boeing Field.

    E-002 was, as I remember, was the static proof test airframe.

    E-003/N327ML/N21LF:
    This was our first data bird and had a lengthened fuselage compared to E-001. First flight was June or July 1982. My logbook detail doesn't show if I chased E-003 first flight in our T-33 or E-001. N327ML was re-registered N21LF sometime between 6/7/84 and 6/23/84. Rumor had it that there was no love loss between our CEO at that time and Moya Lear and that the N number was changed to spite Mrs. Lear. The blue stripes were also repainted green to reflect the national color of Saudi Arabia (Prince Sultan Bin Salman Al Saud, nephew of the King and a major investor, was a friend and business associate of the CEO). My first flight in N327ML was on 11/11/1982 and last flight in N21LF was 5/10/85 with Dave Anderson. The photo of E-003 at the Frontiers of Flight Museum shows that the data boom has been removed from the nose.

    E-004 thru E-008:
    My recollection is that these numbers were reserved for static and subcomponent test articles.

    E-009/N98LF:
    Bob Jacobs was my flight test engineer for the first flight of E-009 on 12/15/1984. My last flights in N98LF were from 4/22/1985 thru 4/24/1985 when Dave Anderson and I flew to Houston Hobby to give an orientation flight to Prince Sultan. He was in training with NASA and later flew on the Space Shuttle. As pointed out in a previous, N98LF is suffering gross neglect by the FAA in the back lot of their OKC facility.

    Prop noise? Simply stated...dirty air entering the prop disc.

    John Penney


    -----------------------------


    From Here; Lear Fan(s) - Page 4 - Aviation Airshow Air Race Photography Discussion
     
  13. Feb 5, 2011 #13

    Topaz

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    At believe at least one of the LearFan airframes was used for crash-impact testing at a NASA swing/drop facility as part of a project to characterize composite airframe behavior in crashes. Can't seem to find the video on YouTube anymore.
     
  14. Feb 5, 2011 #14

    Toobuilder

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    There is one that often flies the PMD VOR (always figured they were going into BUR) at around 11:30 - noon. I walk at lunch time and I can pick it out right away just by the sound.
     
  15. Feb 5, 2011 #15

    Tom Nalevanko

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    I think that the best description of the Piaggio P-180 noise is 'annoying'.
     
  16. Feb 5, 2011 #16

    Monty

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    There is a Piaggio that occasionally operates around here. It has flown over my house several times. It was pretty high and climbing....sounded like two very angry hornets on crack in close formation.

    I've heard it fly over on a completely overcast day...and I knew EXACTLY what airplane I was hearing....it is....shall we say..."distinctive".
     
  17. Apr 15, 2015 #17

    voldpilot77

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    Actually not correct, the Lear-Fan passed pressurisation tests in excess of FAA requirements and flew perfectly, the FAA claimed to have found microchips in the transmission and then asked for a further certification proofing which meant months of work beyond the already overspent budget so we were forced to wind up the company. (I was the Lear-Fan Fuselage lead designer)
     
  18. Apr 15, 2015 #18

    BJC

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    Welcome to HBA, VOP.

    Semi-retired must mean that you still are doing some design. Your personal E-AB project?


    BJC
     
  19. Apr 16, 2015 #19

    bmcj

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    Sorry for replying to an old post, but I saw the LearFan operating several times at Reno Stead in the 80's and, yes, it did seem like a quiet plane.
     
  20. Apr 18, 2015 #20

    autoreply

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    Care to elaborate some more about the Learfan? It's for sure an interesting design and I've never found a truly satisfying answer to why it didn't work out.
     

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