Flying High

[Bennie Vorster]

What will the dangers be of flying at a higher altitude. Our area is 4170 ft about sea level and I found that flying at 4300 ft I normally clear power lines and Radio masts in the area. When flying cross country I usually fly at 5800 or 6 300 ft. Is this to high and what are the dangers involved? The previous time I cleared a mountain at 8400 ft coz I was scared to encounter turbulence and it feel like I'm the only freak out here.

[cornell]

Hi Bennie

Have not been in the Law books for a long time so this is from memory


Higher than 10 000ft not longer than 1 hour without oxygen

Higher than 12 000ft must be on Oxygen.

Flying higher over a mountain or hill is better to avoid Berg winds. This you can identify by Rotor or Lenticular clouds on the lee ward side of the mountain but if the air is dry there will be no clouds. Always try and cross a mountain or hill with a 45 degree angle so if there is berg wind you can turn away from high ground quickly. The up and down draughts can be so severe that your aircraft will not be able to get out of it. Also remember that you Altimeter over reads in these conditions so that's why higher is better.

Flying higher is always better for visibility and safety in a engine out you would have much better options and radio will be better and you would not make a loud noise on the ground.

Flying at 130ft of the ground leaves you with no options if things go all wrong. The only thing of flying higher is that you will fall longer (Which is a good thing).

Also Wind shear you would not easily recover from a 130ft. As wind shear is a sudden change in wind direction sometimes by 180 degrees by 30 knots some aircraft will not outperform that.

Flying high is better not lower that 1500ft over the highest obstacle in a 5nm radius in a cross country and when flying over hills or mountains in windy conditions not lower than 3000ft over the highest obstacle.

[GR8-DAD]

Bennie, where we fly it is mostly mountainous terrain and we were taught, as rule of thumb, to clear the mountains by at least 50% of the HEIGHT of the mountain to avoid all the dangers that Cornell mentioned. However the capability of your craft and your experience must also be considered.

[Bennie Vorster]

OK but what dangers are there in flying high with in the aircraft limits?

[Morph]

There are no dangers expect if you go too high you can suffer from lack of oxygen and you would probably freeze.

As far as the plane is concerned the higher you go the less the performance. eventually you will reach a ceiling where the plane cannot climb any more.

My plane flies at sea level and the carbs are jetted for it. At sea level I get 700 to 1000 fpm climb depending on density altitude. At 8500 I only get 300, decreasing as I climb higher.

Technically the only thing that can go wrong I suppose is potentially carb icing, if you are in the Hot, High and Humid conditions you could be pushing your luck. I have not encountered this at all so can't talk from experience. Talk to the Durban guys who seem to pick this up regularly.

[Smiley]

One small thing I feel when flying at about 10000ft is that the wing becomes a little bit heavier when turning, but that's not a problem. I think it's just the density of the air up there..??

[Thunderboy]

Do semicircular rules apply (odds & evens)? I know we apply them at 1500ft AGL but we inside JHB CTA do they apply outside CTA's ?

[Morph]

Thunderboy,

It comes in to play once you exceed 1500ft AGL and you are outside the control of a tower. Once above this altitude you have to tune to the local information service freq, change QNH to 1013.25 and apply the rule, evens west and odds east

[Smiley]

Do semicircular rules apply (odds & evens)? I know we apply them at 1500ft AGL but we inside JHB CTA do they apply outside CTA's ?

Yes!

The semicircular rule (also known as the hemispheric rule) applies:

Track 000 to 179° - odd thousands (FL 250, 270, etc.)
Track 180 to 359° - even thousands (FL 260, 280, etc.)
At FL 290 and above, 4000 ft. intervals are used to separate same-direction aircraft (instead of 2000 ft. intervals below FL 290), and only odd flight levels are assigned, depending on the direction of flight:

Track 000 to 179° - odd flight levels (FL 290, 330, 370, etc.)
Track 180 to 359° - odd flight levels (FL 310, 350, 390, etc.)
Next time you fly, listen to the captain say what flight level you're at - it will obey this rule according to what direction you are flying in. On the return trip, notice the altitude difference (e.g., FL 290 or FL 330 eastbound, and then perhaps FL 310 or FL 350 westbound).

Countries where the major airways are oriented north/south (e.g. New Zealand and France) have semicircular rules that define a North/South rather than an East/West track split.

In the U.S. and Canada, note that the foregoing information applies to flights under instrument flight rules (IFR). Different altitudes will apply for aircraft flying under visual flight rules (VFR) above 3000 AGL.

[Morph]

Remember Smiley for VFR use the half thousands i.e west 2500, 4500, 6500, 8500, 10500 etc, and east 1500, 3500, 5500, 7500, 9500 etc

[Smiley]

Remember Smiley for VFR use the half thousands i.e west 2500, 4500, 6500, 8500, 10500 etc, and east 1500, 3500, 5500, 7500, 9500 etc

Yes
Versions of this apply to IFR in the UK inside controlled airspace and generally in the rest of the world

[cornell]

There are no dangers expect if you go too high you can suffer from lack of oxygen and you would probably freeze.

As far as the plane is concerned the higher you go the less the performance. eventually you will reach a ceiling where the plane cannot climb any more.

My plane flies at sea level and the carbs are jetted for it. At sea level I get 700 to 1000 fpm climb depending on density altitude. At 8500 I only get 300, decreasing as I climb higher.

Technically the only thing that can go wrong I suppose is potentially carb icing, if you are in the Hot, High and Humid conditions you could be pushing your luck. I have not encountered this at all so can't talk from experience. Talk to the Durban guys who seem to pick this up regularly.

Carb Icing can happen from 30C so it's not about flying high

Thunder boy remember you have a Transition level for Climbing and a Transition Altitide for Desending.

[Duck Rogers]

What will the dangers be of flying at a higher altitude

You have much more time to think on the way down about how hard you gonna hit the ground when something goes wrong...

On a serious note, most everyone has answered your question by now. I personally don't like flying too high. I suppose we all have our comfort zone as to what altitude we like. I prefer 500 to 1000 ft AGL. Anything over that I don't like. I don't mind it, but I don't necessarily feel comfortable about it. At my preferred altitude I'm almost always out of the way of faster traffic :D

Duck Rogers

[cornell]

When I used to fly the C206 12000ft use to be the norm even for short hops Ladysmith to Newcastle even 14000ft to avoid some weather in a twin.

[RV4ker (RIP)]

Toss up between time to climb and speed. Higher you go the longer it will take to get up there as engine loses power unless Turbo. My RV's IO-360 will give me 21" (Cruise setting) MAP up about FL095, then it starts comming down. The Albat will deliver almost full power to FL180. Once up there the speed should be higher (in zero wind conditions) and air should be calmer. Don't know of many in trikes who go that high x country, but for most x county bliks it is the norm (well it as pre ATC charges days).

On recent flight I was getting 165kts at 6500'. At FL115 I got 208kts (GPS) with same power settings as wind above 10000' was reported at 25kts gusting 32. (Had to reduce power for decent). Made up 12 mins on flight time. Obviously if was going in opposite direction would have remained low to get "under" the wind and not "waiste" time climbing...

Don't think it would make a huge difference in trike, other than FREEZE FACTOR... Loss of power would be quiet high and rate of climb would decrease significantly... Definition of high is relative. Most trike jocks I would hazzard to say would call 2000' AGL High, while most blik boys (3 axis) would not?

My 2c - Depends on mount and mission....