Perfect Mooney Landings – Every Time! Utilizing the Runway Expansion Effect
There is an anomaly that some call the “Runway Expansion Effect”. While on approach, as you near the runway, its trapezoidal shape naturally grows in the windscreen. Its growth expands geometrically, but the last eight to ten seconds before touchdown, it defies its previous geometric growth. For instance, here is how the runway looks when you’re 18 seconds, 16 seconds, and then 12 seconds before touchdown. It looks quite normal in its growth.
Then, referring to the graphic below:
At 10 seconds, it really starts to “expand”, and at 8 seconds the runway is downright massive. That’s quite a picture change in just just four seconds.
Conveniently, when the runway begins to expand, defying geometric logic at about 10 seconds, that’s also when you should begin your flair. By the time 8 seconds rolls around, you should be in the flare.
The assumptions to make this work:
1) You’re a precise pilot and
2) You have stabilized your approach at your aircraft’s stall speed (VSO) + 30%. The formula is sometimes referred to as 1.3 x VSO.
For Instance . . .
The M20K POH specifies 75 knots for a landing approach speed with flaps full. Using the VSO + 30% formula, the M20K, at max gross weight of 2,900 pounds, has a VSO of 59 knots. 1.3 x 59 gives us 77 knots – very close to the POH specified approach speed.
The M20C specifies 80 MPH on final. Its VSO is 57 MPH. 1.3 x 57 = 74 MPH; just 6 knots slower than the POH 80 MPH.
What about Landing at Lighter Weights?
In the military and in the airlines, burning a ½ ton of fuel has a big effect on approach speeds. That’s not the case in Mooney Land. Let’s use the M20K as an example. After a three hour flight, the K will have burned 45 gallons or 270 pounds. Instead of a gross weight of 2,900 pounds, the M20K now weighs 2,630 pounds and the VSO has decreased a whole two knots, from 59 to 57 knots. 1.3 x 57 = an approach speed of 74 knots. That’s only three knots slower than max gross weight approach speed of 77 knots. If you can read three knots and nail it, we at TMF are very proud of you. The M20C POH doesn’t specify a VSO for lighter weights. However, after a three hour flight, you will have only burned off 30 gallons or 180 pounds. An 80 MPH approach speed should still work very well.
The moment you notice the “Runway Expansion Effect”, you should pull your power to idle, if it’s not already at idle, and raise your nose level with the runway.
As you begin to settle, raise the nose further and put the top of the cowling on the distant horizon. Continue with back pressure on the elevator to keep the top of the cowling on the distant horizon.
Here are a few pictures to give you an idea of what the runway will look like as it “expands”:
Bringing the Power to Idle
I have learned that in calm winds, reducing power to idle when I feel that I’m 50 yards from the threshold works very well. In stronger winds, 10 to 20 yards prior is a better idle point. Maintain your aim point, just beyond the landing threshold, and begin your flare when at the 10 second point; when the runway begins to expand. If you are having a difficult time making consistently great landings, try it. You can thank me later. Jim