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Ted
If the power output promised is accurate 22000 will be the max speed altitude but you (if the output is normat) get a normal power of 75% or 65% the max cruise speed altitude will be significantly higher that 22000. BUT (the big maybe) there are many factors that make this rule flexible. A few of the most common problems are with the turbocharger. The first big bugaboo is turbo stalls (air is no longer flowing thru the turbo correctly either hot side or cold side). These can be minor loss of power or catastrophic loss of power. The issue primarily that automotive engineering normally deals with atmospheric
pressures only down to about 60% of sea level pressure. One half ot the atmospheric is below 18000 feet. Then we get into controls, can the waste gate ever close completely as this makes for a problem called bootstrapping. In aircraft designs the waste gate is prevented from fully closing which still exposes one to the problem but minimizes the intensity of the Issue. Then we get into more frustrating issues. This has to do with the matching of the power plant and the normal performance range of the turbocharger. Leaving that behind for a second a common problem is the spark generation system, with altitude the air resistance drops and arcing becomes a greater and greater problem. It took years to finally mostly eliminate this kind of
problem. Pressurized mags, better insulated leads, and better spark plugs finally improved this area of reliable power. Once again automotive does not normally have these problems because they do not go high enough.
But back to your question, "What is the airframe limit for N540TF?" The first airframe limit is going to be the lack of adequate directional stability, which I have mentioned before. They have a saying in aircraft engineering 'power is destabilizing'. This is very true in the case of the LIV as it has weak directionally stability so adding power shows up first in direction stability issues. I mentioned early on that you will probably need to add a ventral fin. Not the dual fin that is being sold to Lancair owners but a single fin about 3 feet long
and 8 to 10 inches deep. Every over powered Lancair that I have flown has needed it but some owners have chosen to not to do so. The result is the aircraft is almost uncontrollable with the abrupt loss of power (either a throttle pull or engine failure) and this is just the time you what another problem. It is especially nasty in turbulence. What causes this is after a power reduction the propeller up front produces drag which has the effect of a big surface in front of the cowling, which over powers the limited vertical fin and rudder. The bottom line is the airplane is experimental and some or all of these issues will appear plus some slightly unexpected issues too. ie door not opening...
Sorry I went on so long but there is a lot more issues requiring planning.
Jack
From: Ted Noel <tednoel@cfl.rr.com>
To: lml@lancaironline.net
Sent: Saturday, April 6, 2013 9:47 AM
Subject: [LML] Re: FL270
I thought the cabin pressure relationship, 8,000' cabin at FL280 was
the emphasis in the manuals. Of course, that presents an interesting
question: "What will be the airframe limit for N540TF?" It has 600
hp, and is supposed to be able to maintain sea level power to FL220.
Hmmm
Ted Noel
On 4/5/2013 12:24 PM, pete@leapfrogventures.com wrote:
I
believe the service ceiling is FL280. I have had my ES-P up
that high twice. While it was a slow climb above FL250, it
was still well over 100 ft/min at FL280. You IV guys should
have no problem getting that high. I think only RVSM limits
you from going higher.
Pete
From:
William A. Hogarty [mailto:billhogarty@gmail.com]
Sent: Thursday, April 04, 2013 7:50 PM
To: Lancair Mailing List
Subject: Re: [LML] FL270
Someone told me that the "service
ceiling" is defined as point at which the aircraft, at
full power, cannot maintain
Another someone mentioned that the IV-P
was limited in altitude by engine parameters. If that is
correct, then each
aircraft would probably vary in max
altitude by builders skill and technique in building.
Finally, he who builds the lightest
plane with the minimum accessary drag and the tightest
cowling, might be the winner.
..........sounds like it might be an
interesting competition.
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