Light Sport Aircraft Survey

[Cub flyer]

one other thing on auto mixture

With the Lycomings if you cruise under 65% power you can lean until they quit and won't do damage.

Just fly below that power setting and you can't mess it up.

I usually placard the 65% settings for each altitude on a card somewhere and fly a lot by that. Or if I'm in a hurry go higher power settings and lean till it is rough. Push mixture in till it's smooth and add 3/8 for grandma.

Keep it simple.

the old Stomberg carbs for the ancient continentals would automatically lean by the air pressure on the float bowl. No moving parts. Thats how a Cub can get to 10,000ft. Some also had a mixture knob to lean even further but they were wired off because of accidents where people expected an idle cutoff but there was none.

[glyn]

you know.. not only are there some great ideas (club flyer) im learning as this goes along. that's the best thing about these web forums. the amount of information you can pull from.

[Cub flyer]

Did the students get any results from the survey. It would be interesting how it went.

Wasn't there another manufacturer who did a similar survey a while back. wonder how it came out??


Here's another tidbit. the hottest EGT displayed on the guage might not be the hottest. Depending on probe condition, contact resistance, position in the exhaust pipe.

first to peak is what is important. coolest indicated temp could be the leanest cylinder and first to peak. You don't know. That's why the good alcor EGT guages have no temperature labels. just hash marks every 25 degrees. You just lean to peak EGT, set the needle to the star with the adjustment knob, enrichen the desired amount and watch for changes after setting the mixture. simple. no electronics needed, just a single thermocouple.

for climb just set climb power after takeoff, look over at your EGT reading and use the mixture knob to maintain that reading all the way up. then lean for cruise. If that indication was not too lean at sea level it won't be at 6000 ft Who needs automatic. I'd rather a simple knob than worrying about bellows and springs I have no control over.

The manufacturer needs to determine which is the leanest and install a single probe in that pipe. Same with CHT. determine which cylinder is hottest. Might be better than everyone watching all the bars go up and down, flashing lights, beeping. I feel like a flight engineer interpreting some of these monitors. Never had a problem without them. Keeping all those probes working is a pain and adds more weight/ expense.

Testing by the manufacturer and good baffling is the key. We're making these airplanes and flying way more complex than needed.

sorry off topic but the students tend to try to overcomplicate things.

[pilotjohn]

MAP/RPM/Power

For the Rotax 912 a good estimation is:

5800 RPM and 30 inHg is 100% power, so 30*5800=174000 is full power.

5500 RPM and 23 inHg (7000 feet WOT) is about 73% power (126500.)

RPM*MP / Max.RPM*30 = % Power

This is a good rule of thumb without taking into temperature and non-linear power output of most engines etc.

[Cub flyer]

Thats neat. never saw it calculated that way.

I'm installing a JPI in a customers airplane that calculates % hp and other things for a supercharged engine. Will be interesting to see how it works.

I'll probably have to eat crow and say I like it.

[pilotjohn]

A quick chart showing the approximate % power (ignoring engine characteristics and temperature) using RPM vs MAP.

Code: Select all

%               MAP                                                            
                30    29    28    27    26    25    24    23    22    21    20    19    18    17    16    15

RPM 5800        100   97    93    90    87    83    80    77    73    70    67    63    60    57    53    50
    5700        98    95    92    88    85    82    79    75    72    69    66    62    59    56    52    49
    5600        97    93    90    87    84    80    77    74    71    68    64    61    58    55    51    48
    5500        95    92    89    85    82    79    76    73    70    66    63    60    57    54    51    47
    5400        93    90    87    84    81    78    74    71    68    65    62    59    56    53    50    47
    5300        91    88    85    82    79    76    73    70    67    64    61    58    55    52    49    46
    5200        90    87    84    81    78    75    72    69    66    63    60    57    54    51    48    45
    5100        88    85    82    79    76    73    70    67    64    62    59    56    53    50    47    44
    5000        86    83    80    78    75    72    69    66    63    60    57    55    52    49    46    43
    4900        84    82    79    76    73    70    68    65    62    59    56    54    51    48    45    42
    4800        83    80    77    74    72    69    66    63    61    58    55    52    50    47    44    41
    4700        81    78    76    73    70    68    65    62    59    57    54    51    49    46    43    41
    4600        79    77    74    71    69    66    63    61    58    56    53    50    48    45    42    40
    4500        78    75    72    70    67    65    62    59    57    54    52    49    47    44    41    39
    4400        76    73    71    68    66    63    61    58    56    53    51    48    46    43    40    38
    4300        74    72    69    67    64    62    59    57    54    52    49    47    44    42    40    37
    4200        72    70    68    65    63    60    58    56    53    51    48    46    43    41    39    36
    4100        71    68    66    64    61    59    57    54    52    49    47    45    42    40    38    35
    4000        69    67    64    62    60    57    55    53    51    48    46    44    41    39    37    34
    3900        67    65    63    61    58    56    54    52    49    47    45    43    40    38    36    34
    3800        66    63    61    59    57    55    52    50    48    46    44    41    39    37    35    33
    3700        64    62    60    57    55    53    51    49    47    45    43    40    38    36    34    32
    3600        62    60    58    56    54    52    50    48    46    43    41    39    37    35    33    31
    3500        60    58    56    54    52    50    48    46    44    42    40    38    36    34    32    30
    3400        59    57    55    53    51    49    47    45    43    41    39    37    35    33    31    29
    3300        57    55    53    51    49    47    46    44    42    40    38    36    34    32    30    28
    3200        55    53    51    50    48    46    44    42    40    39    37    35    33    31    29    28
    3100        53    52    50    48    46    45    43    41    39    37    36    34    32    30    29    27
    3000        52    50    48    47    45    43    41    40    38    36    34    33    31    29    28    26

[Cub flyer]

Piper has charts for each RPM and altitude as to what MAP gives what power setting for constant speed airplanes.

With the ground adjustable prop on most Rotax installations there are a lot of variations.

If you only have one prop pitch then you can narrow it down a lot.

Nice chart. Follow how many different RPM's give 65% power.

Not all are smooth and not all are the best but there is a happy medium in there somewhere.