172SP, Hot and High

[paulo]

Apologies for using a new thread to seek opinions...

I've narrowed down my options on renting for a Grand Can trip and fancy the VFR corridors which require a high density alt, 11,000ft-ish transit. Four up in a 172SP is ??? (a) Don't bother (b) Hmmm. Depends (c) Go for it!

Answers on a, err, post! Cheers. :-)

[182 looks like it's out of my league hours wise for a rental - I'm not 100 PIC - a bit annoying as I think I'd be safer in the 182 with sufficient dual, vs. something weedier with a 'lower' previous exp. requirement]

[Keef]

It'll depend on the weight of the 4, but don't forget the need for oxygen, too, if you spend long up at the higher corridor altitudes. 11000 is OK, but some of those corridors (from memory) goa fair bit higher. Not got the charts here, so can't check.

I think you'll be pretty lucky to get up there 4-up in a 172. I did the trip 2-up in an Arrow a couple of years ago, and that was getting a bit breathless at 11000 (density altitude was more like 13000).

[paulo]

Keef - Thanks. I was beginning to factor oxygen into my plans. I know from snowboarding that that kind of alt. is a bit of a gasper.

The SP is a 180hp job, but whether that's enough extra hoof for the task I don't know (sounds a bit marginal, but the renter person was happy to run with it??? hmmm)

[slim_slag]

Density altitude doesn't really affect human physiology, only mechanical physiology :) You can safely assume that the air in your alveoli is 36.9 C and 100% saturated with water at any altitude your plane will get to. Your engine and wings have a different view on the world.

If flying the corridors, you have to reach a minimum of 10500 flying southish, and 11500 flying northish. You can approach GCN from the north and not have to climb above 10500. The charts will make it obvious.

When you are dragging your knuckles - er sorry, snowboarding - you are exercising, hopefully when at 11500ft in a plane you are not. So that will make a difference. 11500 is still a significant altitude, but for a fit healthy adult living at sea level supplemental O2 is not really required. The FAA regs allow for this, but be aware of the symptoms of hypoxia. I've never known a healthy person to have problems at 11500, but my good lady friend who is a flight nurse and so transports patients at cabin pressures of 8000ish has had to give supplimental O2 to some of the sickies she cares for.

I'd not bother taking off with four in a 172SP and expect to reach 11500 at the temperatures currently found in the Canyon. Good chance you will have to turn around. Even so, there is still a lot of great stuff to see around there at lower altitudes. Get the chart out and plan a route.

PS Paulo. The definition of PIC is different in FAA land. Find the FARs on the web and hunt it down, you might find have a pleasant surprise, and you will also get used to the FARs which you really need to do when you fly in the US. If you can work out the very sensible FAA rules for logging PIC you can give yourself an A+ in FAR_Speak :)

[Sensible]

I've flown at 12,500 ft East to West in the US including the Grand Canyon corridors for several hours without any ill effects whatsoever, not even a headache at the end and I'm not exactly in the first flush of youth or a super fit sportsman but I don't smoke. My passenger didn't even notice any adverse effects either. In my opinion, O2 isn't necessary up to 12,500ft.

4 up in a 172 is pushing it a bit especially if it's 4 heavies. If you are coming out of Las Vegas then you may need to circle to get high enough for the corridor. Density altitude is a problem in the canyon area too. Give a thought to where you are going to land but more especially where you are taking off from if you don't plan on a return to the same airport. a 172 when it's hot and high and has a lot of weight uses a lot of runway! Hope you don't plan on taking too much luggage!

[slim_slag]

Well, this thread got me thinking about an old thread when I presented a rule that you should abort if you are not at 75% of takeoff speed by 50% of the way down the runway. What fun that little spat was, it brought out a few people who really should send their PPLs back and buy one of those invalid carriages to get from A->B :) There was even an ATP who should be ashamed of himself!

I've been waiting for this report to come out. Fatal crash at Sedona (http://www.ntsb.gov/ntsb/brief.asp?ev_id=20030418X00530&key=1). Sedona catches quite a few people out, it's actually quite a nasty little strip. Hot, high, lots of Sunday pilots who also should send their PPLs back, and stupid noise regs make you take off on 21 when they are landing on 3. All uncontrolled.

Several witnesses observed the takeoff roll. They all noted that the airplane did not seem to accelerate and was rolling very slowly as it passed the midfield point. Several of the witnesses noted that the flaps were partially down. The witnesses thought the airplane would abort the takeoff. However, it continued and was still on the ground about 80 percent of the way down the runway.

If the pilot had cut the power and put the brakes on at 50% down the runway, all three would have survived. That is a 100% certainty.

So paulo, if you are going to be carrying four in a 172-180 at hot high airports, no matter how long the runway is, make sure you understand what the "gotchas" are.

cheers

[Julian]

Paulo,

I took a 2000 Model 172SP to Vegas and the Grand Canyon last November and with 3 up we watched our takeoff roll (just as slim_slags post says), we were happy with it but I think 4 up would have been a different story. It can get VERY hot in that region so I would not chance it.

Under the FARs you are encouraged to use supplemental O2 >10000ft for day and >5000ft for night flying although the CFRs dont require O2 until you have been exposed to alts between 12500-14000 for more than 30 mins and >14000 requires it immediately. Every occupant must have it above 15000ft.

If you are night flying then make sure you take this account, we limited our ceiling to 8000 at night as otherwise you can notice a difference as your vision starts to feel weird! So the IFR route you took to get there may be no good for coming home due to the MEAs required.

The FARs suggest:

15000ft - Pilot performance seriously deteriorates within 15 mins.

18000ft - Ability to take corrective and protective action lost in 20-30 mins.

20000ft - Ability to take corrective and protective action lost in 5-12 mins.

And then Unconciousness!!!!

All these figures are based on a healthy, fit pilot so if you are on medication, ill, etc these times will reduce.

[Brooklands]

Having flown the 172SP, I think four up is optimistic if you're hot and high. Its a shame you haven't got the hours for the 182 as you'd be much better off in it, as the useful load will be about 1100lbs

The useful load in the 127SP is something like 850 lbs (but it depends on the kit fitted), which with four people averaging 12st would only leave you with just over half tanks at max all up weight. This could make getting airborne rather dicey to say the least.

When we went to the fly-in at Sherburn last week, we had to drain fuel out of the 172SP get the weight down. We had three blokes (2 @ 14st and 1 @ 12 st) + flight bags etc, and with full fuel we were 100lb over max weight.

Brooklands