IAS nor TAS. Now CAS is more closely related to IAS than TAS so his
argument has some merit but it is still not quite correct.
Helen
On 3/9/2010 8:00 PM, Bill C wrote:
> Here is an interesting post to another group concerning engine specs and how they effect this:
>
>
> Re: Fastest Light Sport Airplane?
> One thing is to remember is that top speed is limited to 120kts IAS NOT TAS. This is usually related to max continuous RPM of the engine. In other words, an LSA can have an IAS no higher than 120kts when running at it's max contious RPM. Therefore, the fastest LSA should be the one with an engine that can maintain max contious RPM (and thus 120kts IAS) at the highest altitude.
>
> For example, a Rotax 912ULS has a Max RPM of 5800 and a max continous rpm of 5500. at 5500rpm the engine is running about 90% power. The highest altitude it can attain and still run at 5500rpm/90% power is roughly 3000ft. At that altitude, if IAS is 120kts, TAS should be roughly 127kts. If it flies higher than 3000ft it will not be able to maintain 90% power/5500 rpm and thus TAS will decrease.
>
> Now a Jabiru 3300L has a max rpm of 3300rpm but a max continuous rpm of 2850rpm which is estimated at less than 75% of total power. As a result a Jabiru 3300L engine can maintain max continuous rpm of 2850 at and above 8000ft. At an altitude of 8000 feet, if IAS is 120kt, TAS is almost 140kts.
>
> To take it a step further, the turbocharged rotax 914 can maintain its max continuous rpm to as high as 15,000 ft (although as of now, Sport pilots can not fly above 10,000 ft). At 10K ft with an IAS of 120kts, the LSA should be cruising at around 144kts TAS.
>
> All this assumes that the airframe is clean enough to reach the 120kt IAS limit at it's max RPM. For example, a STOL 701 isn't coming close to that speed with any of the above mentioned engines. It is just too slow.
>
> Hope this helps. My numbers are rough estimates.
> Jon McDonald
> Building Sonex #1287
>
>
> --- In Sport_Aircraft@yahoogroups.com, "Bill C"<bczygan@...> wrote:
>
>> Mark,
>> The consensus standards require the manufacturer to certify that it's product meets the definition of a light Sport aircraft. The owner/pilot is responsible for maintaining the aircraft in a configuration that meets the rule. Can you go faster........sure. Light pilot, no baggage, minimal fuel, tailwind, well polished paint job etc. Are there air cops with radar guns checking? Haven't seen one yet. Could you get in trouble for modifying and flying a plane with a different prop, wheel pants, bigger engine?.....sure. Is it likely?...........not very (depending on where and how you fly) but, how's your luck? Crash and injure/kill someone and NTSB will/must check everything, especially an N numbered aircraft. Talked to a guy today who sold an airplane that crash landed 2 1/2 hours later. NTSB contacted him and determined that his method of filling the oil caused the engine out and contributed to the crash. Just my opinions, your mileage etc........
>>
>> Bill
>>
>> --- In Sport_Aircraft@yahoogroups.com, "blueriverday"<blueriverday@> wrote:
>>
>>> Ok, what I was referring to are various aircraft which have been slowed down by modifications such that they will meet the performance limits for LSA. The Arion Lightning, Pipersport, and
>>> Pulsar XP could all easily go much faster depending upon how you
>>> set them up.
>>>
>>> So I guess what I'm trying to ask is...who and when does a plane get checked to assure that it's slow enough? And, should I accidently find myself clipping along at 140kts, would anyone make an issue out
>>> of it?
>>>
>>> ---
>>> Mark
>>>
>>> --- In Sport_Aircraft@yahoogroups.com, "apollonorthamerica"<apollonorthamerica@> wrote:
>>>
>>>> 138 mph or 120 knots is a performance limit Vh set for LSA. This means at maximum continuous RPM listed for the engine you should not be able to go faster than 120 knots (138 mph).
>>>> In light of that fact, your question is not making sense to me at least. By definition a LSA cannot "cruise effortlessly" at 120 knots. That's Vh.
>>>> Abid
>>>>
>>>> --- In Sport_Aircraft@yahoogroups.com, "blueriverday"<blueriverday@> wrote:
>>>>
>>>>> Hello.
>>>>>
>>>>> Is anyone here actually cruising at 138 mph with no effort, and, if
>>>>> so, is there anything other than "obedience" which keeps you from pushing it just a teeny bit faster, say...140?
>>>>>
>>>>> thanks, Mark
>>>>>
>>>>>
>>>>
>>>
>>
>
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