Difference Between Elevation And Altitude?

[unlikeu]

first, i hope this is the right forum. secondly, i am not a pilot (which i am sure will be quite obvious).

my question: is there a difference between elevation and altitude as it relates to aircraft performance? for example, i was reading the specs of a Tecnam P2006T. it has a twin engine service ceiling of 15k feet, and an OEI ceiling of 7.5k feet. Colorado has a mean elevation of around 6800 feet, Arizona 4800 feet, Utah 6100 feet, New Mexico and Nevada around 5700 feet. so does this mean the P2006T would make a poor choice for operating in this region? or does it matter, because elevation and density altitude are not related?

thanks in advance for any insights.


Mike

[FantomZorbin]

unlikeu

Yes, there is a difference between Elevation and Altitude. In the simplest terms:

Elevation is the vertical measured distance of a fixed point (airfield, TV mast etc.) from Mean Sea Level - usually a positive number but may be negative as for Schipol airport.

Altitude is the vertical distance of an aircraft from a specified pressure datum calculated to be at Mean Sea Level.

So, when you're at home you have an Elevation from sea level, when you're flying you have an Altitude.

Hope that helps.

[unlikeu]

yes that is helpful, thanks. i am still wondering though if the Tecnam P2006T would be a poor choice (due to it's OEI performance) for high elevation regions.

how do piston twin pilots deal with high elevation flying? is single engine performance typically even considered? how important of a factor is OEI service ceiling to pilots flying in high elevation regions?


Mike

[Biggles78]

unlikeu, can you define what you would call a high elevation? My definition may vary from your by many 10s of Flight Levels.

[unlikeu]

sure. as i am gauging it, it relates to the OEI service ceiling of the Tecnam P2006T. many people buy twins for the safety of an additional engine, and since an obvious consideration is "what if one engine fails" should not equal consideration be given to how a particular aircraft performs with OEI.

i was reading up on the P2006T, and it seems to be an excellent aircraft, but when i saw the OEI service ceiling of 7500 feet, i remembered reading about an airport in (i believe) Flagstaff that has an elevation of 7608 feet. that is when i began to wonder if some airplanes should not be operated in some regions due to the altitude limitations a pilot has to consider should he/she encounter an engine failure.

i hope this makes sense to you, as i stated i am not a pilot, and my health precludes me from ever flying. so this is more just a mental exercise for me, but i am really curious as to how these factors effect a pilots choice of airplane and where it will be flown.


Mike

[David Rizzio]

Mike,

Your question might best be answered with another question or two.

"How would a single engine aircraft perform in the same region if there were an engine failure?"

and

"Does that make the aircraft a poor choice for operating in that region?"

Any aircraft can be a "poor choice" under a particular set of circumstances. (The DA-42 with a low battery charge comes to mind.)

[Northbeach]

Mike,

Both you and your questions are welcome here. Aviation is a huge field; nobody has all the answers, certainly not me.

You have introduced several concepts here: density altitude, service ceilings, engine out performance and aircraft suitability choice. I will try and touch on each, not bore you, give out any bad information or get lost in aviation alphabet speak.

The word elevation is usually referenced to a fixed object as in; the elevation of the mountain top, the elevation of the control tower, the elevation of the obstacle at the end of the runway.

Altitude generally refers to height above some reference point attained by an aircraft in flight.

A common reference point is MSL (mean sea level). Looking up the definition of MSL is interesting as it turns out to be the average height of the surface of the sea for all stages of tide over the last 20 years. Pikes Peak in Colorado has an elevation of 14,115 MSL, it’s 14,115’ feet above sea level.

Your Tecnam P2006T noted above has a twin engine service ceiling of 15,000. It would seem that your P2006T could fly over Pikes Peak. However you would find out that it really could not under many conditions.

Cold air is denser than hot air. Dry air is denser than moist air. The denser the air the more power the engine can produce the more effective the wing. The exact same airplane loaded to the exact same weight burning the same gasoline flown by the same pilot would have radically different capabilities if it were operated up in the arctic at subzero temperatures or in Death Valley California in the heat of the summer. The airplane would take off in a shorter distance, fly to a higher altitude and the engines develop more power in the cold arctic air. During the dog days of summer when it is blistering hot in Colorado I seriously doubt the Tecnam P2006T would be able to climb over the top of Pikes Peak. On a crystal clear and cold day in February the same airplane at the same weight would have no problem clearing the peak. This is where “density altitude” comes into play. A working definition of density altitude would be pressure altitude corrected for temperature deviations from the standard atmosphere.

To have a meaningful comparison one has to start out with a standard, that standard is ISA: international standard atmosphere (Sea Level having a temperature of 15C and a pressure of 1013.25 hPA.) So, going back to your airplane it is stated to be able to fly to 15,000 under standard conditions. But if the conditions are not standard; higher or lower pressure and/or temperatures those differences will have an impact on the airplanes performance.

Is your Tecnam P2006T a good choice for Colorado, Utah, Arizona and New Mexico-that depends on many things. What is your budget, how much weight do you want to carry, what are you trying to get the airplane to do. Under many conditions it would be just swell, under other conditions not so good at all. But it is all relative. I fly a 170,000+ lb Boeing 737NG (small potatoes compared to some around here) and I am limited under some conditions coming in (brake energy requirements), going out (second stage climb) and flying over that terrain (enroute drift down) and some of those airports.

I trust you will find something useful in the above comments. They are by no means complete as there is much more information.

Have fun around here, there are many interesting and accomplished people.

[unlikeu]

hey all, thanks for the excellent replies. i think i understand the gist of what you're saying. a given aircraft will perform differently depending on the conditions in which a pilot is flying. so the P2006T is not necessarily a good choice or a bad one for a given region.

again thanks for taking the time to help me understand there is much more to piloting than just raw numbers. :)


Mike