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Thread: Flying In the Mountains

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    Member BARTFRNCS's Avatar
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    Default Flying In the Mountains

    Who here regularly fly in mountains? I do and was wondering if the density Alt get as high as it does in my neck of the woods? The field elevation of my airport is 5280ft MSL. Today at 0945 DA was 7900ft(C172P 160hp). I have followed Troy's posts and there seams to be a lot of mountain type flying in Alaska just wondering if the temps get high enough to pose a problem?

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    Interior Alaska can get hot. Out our way the temperatures are rarely very warm, and most of the airports are less than 1,000 feet elevation. The density altitude is still a noticeable factor though because in the winter we get to fly with -4000 feet density altitude...that's pretty awesome for aircraft performance...if you can keep your toes warm...
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    Quote Originally Posted by BARTFRNCS View Post
    Who here regularly fly in mountains? I do and was wondering if the density Alt get as high as it does in my neck of the woods? The field elevation of my airport is 5280ft MSL. Today at 0945 DA was 7900ft(C172P 160hp). I have followed Troy's posts and there seams to be a lot of mountain type flying in Alaska just wondering if the temps get high enough to pose a problem?
    Rarely, but it's always something to keep in mind . . . . . Occasionally, yes.

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    It seems like the most troublesome factors in Alaska mountain flying are high winds with down-drafts, cold air flow from Ice Fields and Glaciers, and rapid weather changes due to the proximity of the ocean in many areas. While there are not really any real runways much above 1,000 ft MSL, there are sure a lot of lakes at higher elevations.
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    Just as Float Pilot said, some of the high lakes can be problematic in the summer time due to density altitude. Most of the more frequently traveled routes through the various mountain ranges of Alaska are accessed through mountain passes that are lower than 3500'. Merrill pass is considered the most dangerous. It is narrow, with a long narrow canyon approach from either the east or the west. There are a lot of dead airplanes at and on either side of the summit of Merrill Pass and also in box canyons that were mistakenly flown into by pilots thinking they were heading into Merrill Pass. The summit is a narrow rocky vee shape at 3180'.


    Merrill Pass connects interior Alaska with Coastal Alaska (Cook Inlet) through a long narrow canyon with high mountains on either side. Consequently there is very often a pronounced pressure differential between the coastal side of the Alaska Range and the interior side.
    This can result in a constant and sometimes severe downward flow of air as you approach the pass with a head wind, even from several miles away on a clear day. On a hot summer day with a loaded airplane, this can be very troublesome to say the least.

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    I guess I have to disagree with Monguse on this one. My recollection is that the floor of the Merrill lPass lies around 2,400-feet MSL, and the sharp ridge just south lies at around 4,200-feet MSL. It's been a while since I've been through there, though, and I'll bow to ohis statement about elevation. More than that, and after probably more than 200-trips through that pass, I still have to consider both Shellabarger and Mystic Passes as much more dangerous flight routes.

    Monsuse is certainly correct about winds and their effects at Merrill and other passes.

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    For Merrill Pass elevation one website says 3180' another says 1014m or 3326'
    Merrill is more frequently travelled than either Shellabarger or Mystic Passes.
    I think the reason the FAA considers Merrill Pass the most dangerous is because there have been more airplane crashes there and because of attempts to get there than any other pass in Alaska.
    There are at least 13 known crashes visible within a short walk at and on either side of the summit. There are others in box canyons associated with Merrill Pass.

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    I like Merrill Pass, but my minimums are pretty high for going through there. I have to see cloud bases at 4500 feet or higher, and winds that are less than 25 kts at Iliamna and Stony River. Otherwise...no thanks. I've only been through five or six times. Each of those was a time when Lake Clark Pass was closed with fog on the deck and Merrill showed high clouds. I am not so interested in heading through Merrill with ceilings that are low...gets pretty tight down low, and you can't see around the corner very well if you are down there with a dogleg turn like the one at the apex of the pass...
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    Quote Originally Posted by Troy Hamon View Post
    I like Merrill Pass, but my minimums are pretty high for going through there. I have to see cloud bases at 4500 feet or higher, and winds that are less than 25 kts at Iliamna and Stony River. Otherwise...no thanks. I've only been through five or six times. Each of those was a time when Lake Clark Pass was closed with fog on the deck and Merrill showed high clouds. I am not so interested in heading through Merrill with ceilings that are low...gets pretty tight down low, and you can't see around the corner very well if you are down there with a dogleg turn like the one at the apex of the pass...
    . . . . . and at both ends!

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    Any mountain pass should get your attention when that pass is approaching minimums. All are pretty simple when you have the option to go over the top. Winds can make you uncomfortable in the mountains even on CAVU days. The question was about density altitude. There are lots of short and relatively high hunting strips. Temps are usually cool during hunting season. With the mid-70s days we're having in Anchorage the DA at Hood is around 1200'. That's about 1135' above actual. That's pretty much the high norm around here. A few years back we had early July temps in the low 90s. My regular strip's high trees came more into play at those temps, no question. We're spoiled by cool temps and low terrain for the most part.

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    The performance decline from -4000 feet density altitude to +2000 feet DA is the same as going from 0 to 6000 feet in my opinion. It's just that we start from such good performance here in the cold country that the bad DA performance we experience is pretty good compared to Colorado adventuring. I took off on a warm day Saturday with a load and I could feel the difference. But nothing like taking off out of Buffalo, WY in April on a pleasantly warm day...the difference in climb and ground run is pretty obvious.
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    Winter operating advantages are usually limited by required stopping distances on skis. I can get out easier than I can get in. Warm/high ops are quite the opposite.

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    I am not ready to tackle mt flying yet. I think that would be one of the hardest types of flying.

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    Quote Originally Posted by rppearso View Post
    I am not ready to tackle mt flying yet. I think that would be one of the hardest types of flying.
    Actually, it probably isn't. Long contact flights over featureless country tops the list in my estimation, especially for less experienced pilots.

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    Quote Originally Posted by Grizzly 2 View Post
    Actually, it probably isn't. Long contact flights over featureless country tops the list in my estimation, especially for less experienced pilots.
    I was thinking about that as well, flying over the ocean or over something like the sahara desert would probably be harder navigation wise (since there are no visual check points, the ocean you might have islands here and there and the sahara you might have a few little oasis's but that's about it). Not sure weather wise though, weather gets pretty rough in the mts.

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