Date: Wed, 20 Feb 2002 12:17:32 -0500
From: James Frantz <LFrantz@compuserve.com>
Subject: approach speeds
Sender: James Frantz <LFrantz@compuserve.com>
To: "INTERNET:lancair.list@olsusa.com" <lancair.list@olsusa.com>
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>Any advice on mimimum mountain emergency
approach  landing speeds for a LNC2?<

We need to understand that the airplane =

sees only dynamic pressure (IAS) and =

aerodynamically it would not know if it =

was in the mountains or at sea level. =

In other words, the proper approach IAS =

at sea level would be the same at high =

density altitudes for a given GW, CG and =

turbulence condition.  The TAS during =

approach will of course be much higher =

at high density altitudes requiring a =

longer rollout.  Thus the desire to lower
the approach IAS. =


The second important thing to =

realize is that the Lancair =

is not a Champ.  A 1.2 Vs short field =

approach in a Champ will not  =

be safe in a Lancair.  This is another
topic. =


Knowing that the aircraft's stalling =

speed varies with GW, CG and bank =

angle, the approach  speed is =

based on the higher of what =

feels comfortable and provides adequate =

margin above the stalling speed. But,  =

WHAT IS THE STALLING SPEED?

The difference between a short field approach =

and a normal approach is nil in a Lancair.  =

The major difference is the approach =

flight path angle.  Certainly the AOA  =

should be the same. =


In effect, all approaches in a Lancair =

are short field approaches.

As you know, I use AOA to gauge and =

maintain a fixed margin above the stalling =

speed for all approaches. Only the flight =

path angle varies (throttle) depending =

upon field length and approach =

obstructions. All approaches are stable
below 300 feet AGL (no turns or big =

changes in descent rates or IAS/AOA). =


For my particular aircraft,  8.5 degrees =

AOA during approach works =

well and usually results in an IAS of about =

79 to 85 knots. This approach AOA provides
a fixed 6.5 degrees  AOA margin above
the critical angle. These numbers will not
be the same for your aircraft.
  =

For my Lancair 360 this 8.5 degree AOA for =

all approaches provides enough energy to =

stop the descent in the flare without excessive =

float down the runway with the engine at idle =

regardless of GW or CG.

Every custom built Lancair  will be slightly =

different and airspeed errors will vary.  In =

addition, each pilot will have to establish =

their own comfort level.

Finding a good approach IAS is =

like asking what IAS the aircraft stalls at.
It depends upon GW, CG, bank angle and =

other factors and must not be considered
a constant --- =

Nor does the bottom of the green =

and white colored radial on your IAS meter =

tell you where the aircraft stalls!!!!

Many of our fellow Lancair pilots that perished =

in fatal accidents briefly forgot about the =

limitations to flying IAS, nor were they
protected with an AOA (stall) warning.

Tip - For aerodynamics think AOA.  For speed
think GPS. For FARs think IAS.

Jim Frantz
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