On Tuesday, January 21, 2014 3:41:35 PM UTC-8, Bravo Zulu wrote:

"I read that is the minimum altitude to avoid a land out is “normally 500’ with a “penalty zone” of 200’ more. I am simply suggesting that the rule could be improved by adding 300’ to the fixed 200’ as a “penalty zone”. That would preserve the accommodation for instrument error and add an additional measure of safety. It would also make the accumulation of penalty points for a slightly low finish more gradual. My suggestion of a 500’ “penalty zone” was just an example. The RC could pick another number if it were more efficacious. The bigger it is the more gradual the accumulation of penalty points would be. The effect is that for a small error in arrival height there is less incentive to attempt a low save. Finding oneself 200’ lower that intended is more likely than being 500’ lower."


Deep breath. Lots to discuss here.

In the interest of exposing some of the richness of the issues for those of you who are interested enough to dig into the actual details that inform these decisions, here we go.

There are three main objectives for setting rules around finish height and then a bunch of considerations. In rough order of priority:

1) The top objective is to make sure that pilots set up enough altitude buffer to get home without hitting the dirt under most scenarios of unexpected sink, headwind, etc. A decent MFH does this pretty well so long as it includes a penalty that costs more than the speed points lost from stopping to climb in a weak thermal. (Otherwise pilots gain points by ignoring thermals below the break-even climb rate for the penalty gradient). This is the highest order pilot decision - setting up the glide is at the top of the final glide decision chain. The penalty is fundamental - without a penalty structure MFH is practically meaningless. If you want to have all pilots set a 1000' arrival you need around 100-200 points per 1000' at stake to create an incentive in favor of climbing in a weak thermal rather than pressing on.

2) A related, but separate, second objective is to not create a points temptation to go for the finish cylinder at a height from which you cannot safely make the airport - instead of picking a decent field while you have a little altitude. This is mostly a "glide gone wrong" or "glide that was never right" scenario and is a totally different pilot decision from #1. This minimum safe altitude is, as has been pointed out, around 400-500' a mile out, depending on the airport configuration. Therefore, the penalty for 500' or below needs to be around 400 points to get rid of the points incentive to press on. That means you need to spread 400 points of penalty over the difference between MFH and 500 feet. That's 0.8 points per foot for a MFH of 1000'. If you set a 700' MFH you need to use 2.0 points per foot and if you set a 501' MFH it's 400 points per foot.

3) A third objective is to not encourage pilots to thermal low. This objective is subordinate to the other two in part because it conflicts with the other two and because it's pretty clear that having everyone finish at zero feet is not a good solution to not having people thermal low. Any MFH with a penalty will yield some situations where a pilot would prefer no penalty to any penalty and will try to climb up to get out of the penalty zone. The old rule, BTW, also had this feature only with fewer points at stake. It is not clear how many pilots would reject a climb to avoid a 50 or 100 point penalty but would take the same climb when the penalty is 400 points, maybe some, but experience indicates that many pilots would take a climb at 500' for to save a small number of points.

Then there are additional considerations that shape the final solution. People hate complexity so having a variable penalty based on MFH was set aside as was restricting the MFH to 1000' because some sites need MFH lower mostly to accommodate ridge tasks. One to two points per foot was viewed by many pilots as draconian small misses so a more gentle penalty was put in place for the first 200'.

After all these additional considerations you are left with basically no room for further graduation of the penalty for MFH700' - and a pretty steep gradient even for MFH=1000'.

Also worth pointing out, the old rule only addressed the first objective, not the second or third. The new rule addresses the first and second, but not the third. Adding a 500' hard deck for 5+ miles around the finish (either to the current rule or some steeply graduated variation) would address the first two plus mitigate the third quite a bit because you'd push the problem out so far that any pilot who is facing it is already in a landout situation. Not sure the pilot community is supportive of a hard deck, even a small one around the finish, but I'd be curious to know if it's viewed as worth it in order to reduce the low thermalling temptation.

9B