Tips on departing KMMH Mammoth in a non-turbo single engine aircraft

[MajorTurbulence]

In my cross the country trip to Yosemite around September 8, I would prefer to land and depart KMMH Mammoth instead of the no brainer at KBIH Bishop. I’m in a Pa28-181 which is obviously normally aspirated. I recognize that purposefully staying under gross as much as practical( I think I can keep it at least 100lbs under MGW), leaning for best power, leaving early in the AM to keep the daytime temperatures at their lowest will maximize performance. The likely temperature and pressure altitude will place the performance graph (with and without take off flaps) above that given in the POH, so while extrapolation may be risky, I’d estimate 4400ft without and 3600 ft using 25degrees flaps for a no wind departure over a 50ft object.

A review of the available airport information includes the availability of an Instrument approach directed at runway 27 for arrivals, but obstacle clearance is also an issue on departures with a ridge 3 miles from AER 9. The runway has a 1% up gradient to the west. The ODP uses the Nikol 1 departure procedure calling for 500ft/nm climb for Runway 27 and 370ft/nm for Runway 9, which I’m pretty sure exceed the performance available for my Archer at likely density altitudes. My preference however is to do the arrival and departure VFR. I’ve already analyzed my future departure with similar DA issues for KBCE Bryce Canyon, which I think presents fewer terrain issues.

I’d like advice and information from those intimately knowledgeable with Mammoth, and especially those who have gone there in a similar non-turbo single to hear about their experiences and best practices to get in and out, especially with VFR conditions for obstacle clearance. I would hope that performance is adequate to avoid the close by obstacles in the pattern, and that circling overhead the airport could be done to gain additional altitude to transition to the cruise segment. With the nearby terrain, I’d expect turbulence to be a consideration.

 

[AA5Bman]

I think you’re making it into a bigger deal than it really is. The only critical thing is low winds / no significant weather, and early AM departures. Spent a lot of time there and have been in and out in everything from a 180hp Tiger to a turbo’ed 182 to a normally aspirated 205.

Ignore the IFR approaches and departures - you will not be flying any IFR weather there, or if you are, you are suicidal and/or extremely foolish. My experience is that VFR departures are typically made eastbound with mostly lowering terrain. Watch out for Crowley, the cold water of the lake can make a bit of a sink. Yes, I have had to circle the airport to depart in the Tiger, but it’s not that big of a deal. As an aside, I would probably prefer to depart eastbound with a light tailwind than westbound with a light headwind , due to rising terrain.

Again, your biggest issue will be winds flying in and around the Owens valley (including maneuvering at MMH). Stay away from the big peaks. It’s so scenic that it’s tempting to go in for a close look, but they will create really nasty turbulence. Ask me how I know.

Oh, and yes, leaning is essential.

PS - If you plan on crossing the Sierra, that is worth a discussion. In a non-turbo’ed aircraft, I would really strongly recommend only crossing at Mammoth, just south of the ski area. It’s the lowest point and has the most consistently down-sloping terrain on the other side. Crossing anywhere south of there will have muuuuuch higher passes (13k’) and the terrain on the west side kind of goes down and then back up again, so it’s not all downhill once you get across. Winds can be super nasty through all these passes and is your biggest issue so really watch that. FYI this has all been discussed before on POA, so while I don’t mind providing my experience you may fine a lot by searching google for something like Mammoth Sierra siteilotsofamerica.com

 

[EdFred]

I did BCE full fuel departure with a DA of 11400 in a PA28-180. Takeoff roll didn't seem that much longer. I couldn't outclimb that mesa to the east, but luckily there was this big dropoff to the south.

 

[steingar]

I'm probably wrong in this. Never been to that airport, never even flown out West. But usually, if I really have to question if I can or should safely do a thing I don't do it.

 

[EdFred]

I'm probably wrong in this. Never been to that airport, never even flown out West. But usually, if I really have to question if I can or should safely do a thing I don't do it.

If you never raise questions about something you haven't encountered before, how do you ever learn where your actual limits are or expand your personal capabilities?

 

[MajorTurbulence]

I think you’re making it into a bigger deal than it really is. The only critical thing is low winds / no significant weather, and early AM departures. Spent a lot of time there and have been in and out in everything from a 180hp Tiger to a turbo’ed 182 to a normally aspirated 205.

Ignore the IFR approaches and departures - you will not be flying any IFR weather there, or if you are, you are suicidal and/or extremely foolish. My experience is that VFR departures are typically made eastbound with mostly lowering terrain. Watch out for Crowley, the cold water of the lake can make a bit of a sink. Yes, I have had to circle the airport to depart in the Tiger, but it’s not that big of a deal. As an aside, I would probably prefer to depart eastbound with a light tailwind than westbound with a light headwind , due to rising terrain.

Again, your biggest issue will be winds flying in and around the Owens valley (including maneuvering at MMH). Stay away from the big peaks. It’s so scenic that it’s tempting to go in for a close look, but they will create really nasty turbulence. Ask me how I know.

Oh, and yes, leaning is essential.

PS - If you plan on crossing the Sierra, that is worth a discussion. In a non-turbo’ed aircraft, I would really strongly recommend only crossing at Mammoth, just south of the ski area. It’s the lowest point and has the most consistently down-sloping terrain on the other side. Crossing anywhere south of there will have muuuuuch higher passes (13k’) and the terrain on the west side kind of goes down and then back up again, so it’s not all downhill once you get across. Winds can be super nasty through all these passes and is your biggest issue so really watch that. FYI this has all been discussed before on POA, so while I don’t mind providing my experience you may fine a lot by searching google for something like Mammoth Sierra siteilotsofamerica.com

Thanks, just the kind of information desired. I have surmised that if the winds are 20 kts at Mammoth or more, land at Bishop. If the winds are 10 or less, landing should be OK. What if the winds are 10-20 and pretty much a cross wind, is it common to land on runway 9 to avoid the squirreling winds that are often present on the first 3000ft of runway 27?

The plan is not to cross the Sierras at all, but thanks for the warning. With regards to the Owens Valley, I understand about getting too close to mountains on the eastern, or lee side of those areas with winds from the west, and besides the turbulence, the downdrafts are the issue. But going southbound, is it generally reasonably smooth staying over 395 when the winds are less than 20kts at 12k or so, or is there advantages getting closer to the windside mountains in the valley? I have heard that heading to Trona might be a good waypoint for lunch and negotiating the restricted airspace to the south. I was going to Palm Springs, but may instead head to the east to get to the Grand Canyon and understand the controllers are helpful in opening up more direct routings when the spaces are inactive.

PS: I’ll study up on rotor and mountain wave identification and avoidance.

 

[MajorTurbulence]

If you never raise questions about something you haven't encountered before, how do you ever learn where your actual limits are or expand your personal capabilities?

Exactly!
Your airplane is a great traveling machine, if you use it.

 

[AA5Bman]

What if the winds are 10-20 and pretty much a cross wind, is it common to land on runway 9 to avoid the squirreling winds that are often present on the first 3000ft of runway 27?

FWIW, if you plan your flight right, this won't be an issue because you'll be in and out of there in the early morning and the winds will be calm, which is almost always the case in the morning. But, that said, yes, I'd probably prefer to land to the east in the scenario you described. The airport does have that NOTAM about downdrafts on the east end of the runway when the winds are from the south. I've never really experienced anything noteworthy about that, but I'm sure it does happen. If the winds are squirrely, the go-around is a lot better if you're landing east than if you're landing west.

But going southbound, is it generally reasonably smooth staying over 395 when the winds are less than 20kts at 12k or so, or is there advantages getting closer to the windside mountains in the valley? I have heard that heading to Trona might be a good waypoint for lunch and negotiating the restricted airspace to the south. I was going to Palm Springs, but may instead head to the east to get to the Grand Canyon and understand the controllers are helpful in opening up more direct routings when the spaces are inactive.

PS: I’ll study up on rotor and mountain wave identification and avoidance.

A couple things:

First, it's not that common that you'll see forecasted winds at mountaintop of much less than 20 knots. So I wouldn't stress too much if it's a bit more than that. I would probably personally accept forecasted winds at 12-15k over Lone Pine (for instance) of up to 35 knots without considering scrubbing the flight, partly for the reasons addressed below:

Second, it can be a little counterintuitive, but just because the winds are high up at 12,000 or 15,000', does not necessarily mean it will be windy or turbulent down at 6,000' or 8,000', which is still 2-4,000' AGL in the Owens Valley. To the contrary - the wind is often ripping over the top of the mountains yet perfectly calm at Lone Pine and Bishop and Mammoth, especially in the morning. The worst turbulence I have ever experienced (in my whole life, not just in the Owens Valley) was a day that the forecasted winds aloft were high but the winds were calm at the valley floor. I departed Bishop in crystal clear, perfectly smooth air, 100% dead calm air. Everything was fine climbing through 8,000'. Perfect through 9,000 and still dead calm at 10,000'. I got tempted to go a little higher and the second we hit 11,000 feet it was like absolute chaos. The takeaway is that high winds over the mountaintops don't necessarily "mix" down into the valley, so if the wind is calm or near calm at valley locations - Bishop, Lone Pine, Mammoth, etc - you can often stay well below the peaks and putz along in perfect, crystal clear, dead smooth air.

Third, if you do have west-to-east winds aloft, stay to the east side of the valley and you're a lot more likely to be in rising air. 395 is more on the west side, so more likely to be in descending air.

Fourth, the restricted areas look close together, but the Trona gap is gigantic and easy to navigate through. Yes, they will sometimes give you routings through the restricted areas if they are cold. Don't forget that you won't get "cleared" through a restricted area - they'll only tell you they are "cold" and that is all you need.

 

[N1120A]

Absolutely do not use flaps on a high DA takeoff. 4400' is plenty for a properly leaned plane.

 

[EdFred]

Absolutely do not use flaps on a high DA takeoff. 4400' is plenty for a properly leaned plane.

Even POH says to?

 

[murphey]

For those of us who don't live at sea level or close....rule of thumb is lose10% gross weight. In the 181, that's 240# less than a full load. Everything else metioned here - early morning, watch out for winds, etc. is spot on.

 

[AA5Bman]

Absolutely do not use flaps on a high DA takeoff. 4400' is plenty for a properly leaned plane.

I don't agree with this. But I think it's more a matter of personal preference with a runway as long as MMH unless it's specifically called out in the POH. I definitely would use flaps in my 205.

For those of us who don't live at sea level or close....rule of thumb is lose10% gross weight. In the 181, that's 240# less than a full load. Everything else metioned here - early morning, watch out for winds, etc. is spot on.

Yeah, I agree, figured this kind of went without saying. However, I would rather depart at gross weight on a cool windless morning than 10% under gross on a hot windy afternoon... by far.

 

[N1120A]

Even POH says to?

Does the PA28 POH say to do so, cause I've not seen that. Only short and soft field.

 

[MajorTurbulence]

Absolutely do not use flaps on a high DA takeoff. 4400' is plenty for a properly leaned plane.

I don’t agree with this either as it depends on what you can take from the POH for your aircraft. The conditions expected for my expected arrival on September 8 are off the performance charts in the POH for a Pa28-181. But one can take away some pearls. Just for argument sake, I took an example of 7000ft pressure altitude with 40 degrees F, and full gross weight of 2550 lbs, and no wind at the runway just to keep it clearly on the performance charts without interpolation or extrapolation. With this in mind, the distance to takeoff and reach a 50 ft obstruction height was 4400 ft with no flaps, but 3800 ft with use of 25 deg flaps. The use of flaps is specified as the preferred short field takeoff procedure. While a 7000ft runway at Mammoth is not a short field, if you are trying to use up less runway and get to a 50 ft height 600 ft sooner, this is the way. With regard to safety, what is wrong with using the 25 degrees of flaps, getting off the ground quickly (eliminating the rolling friction and energy loss of the gear), staying in ground effect until reaching Vx or Vy, and then starting your climb and retracting your flaps at a safe altitude as soon as possible to get rid of the drag induced by the flaps?

 

[MajorTurbulence]

For those of us who don't live at sea level or close....rule of thumb is lose10% gross weight. In the 181, that's 240# less than a full load. Everything else metioned here - early morning, watch out for winds, etc. is spot on.

10% loss in weight would equal 255 lbs off loaded from MGW of 2550.

 

[steingar]

If you never raise questions about something you haven't encountered before, how do you ever learn where your actual limits are or expand your personal capabilities?

They're mostly spelled out in my aircraft's operating limitations. If it's within those parameters I go. If not I don't. If I'm not certain it fall within my aircraft's abilities I don't do it.

 

[EdFred]

They're mostly spelled out in my aircraft's operating limitations. If it's within those parameters I go. If not I don't. If I'm not certain it fall within my aircraft's abilities I don't do it.

So what does your POH say about an 11,400 DA take off?

 

[steingar]

So what does your POH say about an 11,400 DA take off?

Don't have it in front of me, but I think I'd look at the performance tables. Probably wouldn't do it. What's so great about that airport?

 

[EdFred]

Don't have it in front of me, but I think I'd look at the performance tables. Probably wouldn't do it. What's so great about that airport?

Well, it's at an altitude of almost 7600 feet, and if you go there in the summer time - like the OP asked about, it ain't going to be in your performance tables.

 

[steingar]

Well, it's at an altitude of almost 7600 feet, and if you go there in the summer time - like the OP asked about, it ain't going to be in your performance tables.

My performance tables go up to 11,500 feet, though not for take off and landing. Still, I can extrapolate. A pity they didn't give you such data for your Comanche. Perhaps they didn't think it could get up that high?

 

[EdFred]

My performance tables go up to 11,500 feet, though not for take off and landing. Still, I can extrapolate. A pity they didn't give you such data for your Comanche. Perhaps they didn't think it could get up that high?

OK, so you extrapolate vs interpolate. So you would be testing and expanding your capabilities and testing something that is unknown.

Lawyers didn't require all that crap to be published in 1958.

 

[steingar]

OK, so you extrapolate vs interpolate. So you would be testing and expanding your capabilities and testing something that is unknown.

Lawyers didn't require all that crap to be published in 1958.

Or I bail on the whole thing and go to a different airport. Like I said, what's so great about that one? When picking up Ruby the tortoise from Allentown I was directed toward a 2,000 foot strip, it was very near to where ether tortoise was staying. 2,000 feet is short for me, and the descriptions of the strip talked about part turf and part asphalt. I couldn't get enough information to assuage my fears, so I decided to land Lehigh Valley instead. Ruby the Redfoot tortoise is now resident in my home office and is being sexually harassed by my boy tortoise Mr. President. Longest turn and burn flight I've ever done. But I don't land there unless I am very certain I can land and get back out. You do you.

 

[AA5Bman]

This thread was fun at first, now it is just:

 

[MajorTurbulence]

Let me try to get this a little bit back on topic by talking a little about my own experiences.

I am risk averse, as is probably evident from my line of initial questioning in the thread, and is probably a good thing for any pilot. Some of us may be limiting our growth by phobias of various sorts, but probably most of us are limited by our lack of experience not wanting to bite off more than the little voice in our heads are telling us is OK. You react with anxiety when you realize you don’t know what you don’t know. It is pretty normal to advance our limits as our foundation of knowledge increases. What I would do now is not what I would have attempted very early in my flying life or even years later. I recall many years ago a trip with the family at full gross from the Northeast US to Cody Wyoming. When I landed at Rapid City in the heart of a heat wave, I realized the DAs were such that the even higher altitude airport at Cody was even a greater performance drain. There were some other considerations as well but I decided to drive the rest of the way to Cody and back a week later. I could have flown it based upon the knowledge I have accumulated since, but I felt the decision was right then for me, and it was the right decision at my comfort level, but it was also foundation building.


So what are we talking about here in this thread. Just because the print in our POHs stop at certain limits does not mean the laws of aerodynamics or the science of internal combustion engines cease at those points. Many pilots successfully visit high DA airports like KMMH or KBCE in a variety of aircraft. We know the service ceiling from our POH, for my Archer2 is 13650ft. So we know our aircraft will fly at the altitudes of KMMH or KBCE or the higher DAs during summer temps. But will the airplane have enough climb capability to take off and climb higher than surrounding obstructions or out climb downdrafts that may be a consideration at mountainous high DA airports. That’s where asking questions before you go, coupled with knowledge of the how much performance degrades at high DA, and what you can do to mitigate that, can increase your knowledge and comfort level. These airports are long enough but do the surrounding terrain and weather/wind allow for a successful departure for your aircraft?

 

[EdFred]

Let me try to get this a little bit back on topic by talking a little about my own experiences.

I am risk averse, as is probably evident from my line of initial questioning in the thread, and is probably a good thing for any pilot. Some of us may be limiting our growth by phobias of various sorts, but probably most of us are limited by our lack of experience not wanting to bite off more than the little voice in our heads are telling us is OK. You react with anxiety when you realize you don’t know what you don’t know. It is pretty normal to advance our limits as our foundation of knowledge increases. What I would do now is not what I would have attempted very early in my flying life or even years later. I recall many years ago a trip with the family at full gross from the Northeast US to Cody Wyoming. When I landed at Rapid City in the heart of a heat wave, I realized the DAs were such that the even higher altitude airport at Cody was even a greater performance drain. There were some other considerations as well but I decided to drive the rest of the way to Cody and back a week later. I could have flown it based upon the knowledge I have accumulated since, but I felt the decision was right then for me, and it was the right decision at my comfort level, but it was also foundation building.


So what are we talking about here in this thread. Just because the print in our POHs stop at certain limits does not mean the laws of aerodynamics or the science of internal combustion engines cease at those points. Many pilots successfully visit high DA airports like KMMH or KBCE in a variety of aircraft. We know the service ceiling from our POH, for my Archer2 is 13650ft. So we know our aircraft will fly at the altitudes of KMMH or KBCE or the higher DAs during summer temps. But will the airplane have enough climb capability to take off and climb higher than surrounding obstructions or out climb downdrafts that may be a consideration at mountainous high DA airports. That’s where asking questions before you go, coupled with knowledge of the how much performance degrades at high DA, and what you can do to mitigate that, can increase your knowledge and comfort level. These airports are long enough but do the surrounding terrain and weather/wind allow for a successful departure for your aircraft?

I did BCE in a Cherokee 180. You have plenty of room to the south to maneuver. Mammoth I have not been to.

 

[MajorTurbulence]

Yes, that last question was rhetorical. I have not flown BCE yet, but my analysis agrees with your actual accomplishment. So far, I like the answers for MMH.

 

[Tantalum]

I was told not to extrapolate performance figures from the graphs.. as that puts you in "test pilot" category. I thought this was also the reason why some airliners don't take off on super hot days in Phoenix because their charts don't go that high.. so they wait. Isn't this the standard examiner question "it's you and 3 guys at Lake Tahoe, it's 95 degree in the summer and you each weigh 200 lbs. Tell me your performance" .. and then you say "I don't understand, the POH doesn't go that high" .. and you put two and two together..

Just follow the POH and add a safety factor to it. KMMH is not a big deal, L35 is much more "challenging" on a hot day in a non turbo piston.

..and every take off in the Cirrus is with flaps 50%. You *can* takeoff with 0 flaps, but there is no performance data. I'm not about to become a test pilot when I'm already on the edge of the envelope!

Straight from the G5 SR22T POH

 

[Jeff Oslick]

I have flown into MMH a few times. One of them was in really squirrely winds. I don't recall the exact conditions, but it was moderate turbulence almost down to the ground, with a variable, strong crosswind component (~15+ kts). This was right at the limit of my comfort zone. I'd actually say it was ever so slightly outside my comfort zone with the gusts, but I was willing to take a shot at the landing and see what it would be like. I was giving myself one shot only. If I didn't like it, it would be a go around and back down to Bishop where conditions were considerably better. I got down with a decent enough landing, and "flew" it all the way to the tiedown. The key here is I was 100% ready to do a go around at the first sign that I might not have 100% control on the landing.

Flying that area is some of the most beautiful flying around, but you have to know and respect your limits to keep it safe.

 

[Tantalum]

I have flown into MMH a few times. One of them was in really squirrely winds. I don't recall the exact conditions, but it was moderate turbulence almost down to the ground, with a variable, strong crosswind component (~15+ kts). This was right at the limit of my comfort zone. I'd actually say it was ever so slightly outside my comfort zone with the gusts, but I was willing to take a shot at the landing and see what it would be like. I was giving myself one shot only. If I didn't like it, it would be a go around and back down to Bishop where conditions were considerably better. I got down with a decent enough landing, and "flew" it all the way to the tiedown. The key here is I was 100% ready to do a go around at the first sign that I might not have 100% control on the landing.

Flying that area is some of the most beautiful flying around, but you have to know and respect your limits to keep it safe.

This was my only legit ever divert.. ended up at Bishop. Owens Valley was a proper roller coaster ride that day with 50 knot winds aloft. I was somewhere on short final where I decided it wasn't worth it and went around to Bishop

 

[EdFred]

I was told not to extrapolate performance figures from the graphs..

But what if it's super cold (plastic airplanes not included) and you are on the "good" side of the extrapolation? Do you still not go?
I've gone flying when off the bottom end of the DA charts. Should I have not gone flying then?

Or what do I do in the Comanche where there are no performance charts?

Just making the point that you shouldn't make absolute statements.

 

[Tantalum]

But what if it's super cold (plastic airplanes not included) and you are on the "good" side of the extrapolation? Do you still not go?
I've gone flying when off the bottom end of the DA charts. Should I have not gone flying then?

Or what do I do in the Comanche where there are no performance charts?

Just making the point that you shouldn't make absolute statements.

..and it's not an actual limitation per se. Although the plastic planes I flew did have temperature limitations

Someone else had said to me that it's fine to extrapolate but if you do have an accident expect to get hit with "wreckless operation" or whatever

We're also part 91.. so a totally different ballgame then airliners who won't fly when they're outside of the perf charts

It was a pretty big change when I moved over to the Aztec and all I got was basically a pamphlet!

 

[EdFred]

AFM in the Comanche is like four pages and half of it is Weight and Balance examples

 

[AA5Bman]

This was my only legit ever divert.. ended up at Bishop. Owens Valley was a proper roller coaster ride that day with 50 knot winds aloft. I was somewhere on short final where I decided it wasn't worth it and went around to Bishop

Good example of what I was talking about and generally avoidable. The winds at mammoth are the thing.

If you are departing to the east, and even more or less to the west, there isn’t any terrain that you have to climb out of to get out of there (I mean, westerly you’ll have to circle for sure like if you’re going to Sacramento, but it’s not like there’s some big terrain right at the airport you have to contend with). Your plane will fly at a DA of 10,000, it just wont be pretty so you don’t want winds or other adverse conditions making it worse.

- fly when it’s cool and calm not hot and windy
- fly your air speeds and configurations not your pitch attitudes
- don’t hit anything.

Easy peasy.

 

[denverpilot]

I was told not to extrapolate performance figures from the graphs.. as that puts you in "test pilot" category. I thought this was also the reason why some airliners don't take off on super hot days in Phoenix because their charts don't go that high.. so they wait.

Good luck at Leadville then. You’ll be trucking most airplanes out if you plan on waiting for published data.

As for the airlines no, the rules are different. You may interpolate. They may not.