absolute altitude safety question

[Jonathan Bailey]

What is the minimum safe absolute altitude for a helicopter (flown only for recreational purposes) at a cruising speed say between 110 and 150 knots?

 

 

I ask because my experience in FSX shows that flying low or close to terrain is especially fun and perhaps especially dangerous.

 

Is there anti-collision technology that reduces the risk of a low-flying chopper from crashing into terrain or landmarks?

 

How about an electronic altimeter with a warning voice?

 

How about an auto-pilot function that maintains a preset absolute altitude?

 

One wrong move can cause a captain's ship to run aground.

[apacheguy]

What is the minimum safe absolute altitude for a helicopter (flown only for recreational purposes) at a cruising speed say between 110 and 150 knots?

 

 

I ask because my experience in FSX shows that flying low or close to terrain is especially fun and perhaps especially dangerous.

 

One wrong move can cause a captain's ship to run aground.

 

 

 

 

One wrong move can cause a warrant officer's ship to hit the ground as well.

 

Seriously though, in the army we're generally supposed to be above 200 feet AGL when at cruise speed. If you're flying nap of the earth you're usually at or below ETL.

[Jonathan Bailey]

One wrong move can cause a warrant officer's ship to hit the ground as well.

 

Seriously though, in the army we're generally supposed to be above 200 feet AGL when at cruise speed. If you're flying nap of the earth you're usually at or below ETL.

Are army helicopters equipped with absolute altimeters?

[Flying Pig]

Are you talking about a radar altimeter? Never heard of an "absolute altimeter"

[Jonathan Bailey]

Are you talking about a radar altimeter? Never heard of an "absolute altimeter"

absolute altitude

noun Aeronautics .

the vertical distance between a flying aircraft, rocket, etc., and the point on the earth's surface directly below it, as measured by an electronic altimeter (absolute altimeter)

Origin:

1930–35

Dictionary.com Unabridged

Based on the Random House Dictionary, © Random House, Inc. 2014.

Cite This Source

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Link To absolute altimeter

 

http://dictionary.reference.com/browse/absolute+altimeter?s=t

 

[Flying Pig]

It depends on how you set your altimeter. Are you setting it to give you altitude above sea level or are you setting it to zero, which would give you height above the ground at that particular place. Setting your altimeter to zero doesn't work because as you fly, the elevation of the terrain below you changes. My helicopters have radar altimeters, and a GPS that will give me MSL and AGL. The altimeter itself is set to the barometric pressure. The radar altimeter does give a high or a low warning depending on what I set it for.

[pilot#476398]

What is the minimum safe absolute altitude for a helicopter (flown only for recreational purposes) at a cruising speed say between 110 and 150 knots?

 

 

 

91.119

- An altitude allowing, if a power unit fails, an emergency landing without undue hazard to person or property on the surface.

 

- As long as the operation is conducted without hazard to persons or property on the surface there is no actual number you must stay above.

 

- You must also comply with any routes or altitudes specifically prescribed for helicopters by the FAA (i.e. helicopter specific charts, transition instructions...)

 

If you're a recreational pilot 500' is a good minimum to start with if you want to avoid hitting a lot of stuff,...1000' is even better and what RHC recomends. I generally fly between 800' and 1300' on average.

[aeroscout]

There are many types of altitude you should be aware of when trying to understand the answer to the question you are asking.

MSL

AGL

PA

DA

TA

IA

There are at least 3 cockpit console instruments that display altitude...

RadAlt

BaroAlt

GPS Alt

With respect to BaroAlt, there are 3 settings for it by use of the kollsman window

QFE

QNH

QNE

After you get a good understanding of that, you will most likely be able to answer your own question. You will also be able to answer it in commonly practiced aviation jargon.

Each profession has it's own terms and language. For instance your use of the phrase "absolute altitude" doesn't get much use in the industry.

With respect to

[Jonathan Bailey]

There are many types of altitude you should be aware of when trying to understand the answer to the question you are asking.

MSL

AGL

PA

DA

TA

IA

There are at least 3 cockpit console instruments that display altitude...

RadAlt

BaroAlt

GPS Alt

With respect to BaroAlt, there are 3 settings for it by use of the kollsman window

QFE

QNH

QNE

After you get a good understanding of that, you will most likely be able to answer your own question. You will also be able to answer it in commonly practiced aviation jargon.

Each profession has it's own terms and language. For instance your use of the phrase "absolute altitude" doesn't get much use in the industry.

With respect to

It was in my dictionary.

 

For the purpose of this thread, I am only concerned with the vertical distance between the aircraft and the ground below and not a damn thing else. I am also only interested about civilian aviation, not army pilots. Remember, I am not a pilot, just an enthusiast.

[Astro]

Absolute altitude is the height, or vertical distance, above the surface. Commonly refered to as height "above ground level", or AGL. Jeppesen Private Pilot Manual 2-58

 

For helicpters flying recreationally (under part 91) there is no specific minimum safe altitude, just a set of parameters.

[palmfish]

It was in my dictionary.

 

For the purpose of this thread, I am only concerned with the vertical distance between the aircraft and the ground below and not a damn thing else. I am also only interested about civilian aviation, not army pilots. Remember, I am not a pilot, just an enthusiast.

 

A radar altimeter uses a belly mounted antenna to send a radar beam downwards. It "bounces" off the ground and returns to the antenna to indicate actual height above the ground in feet on a panel mounted instrument.

 

It is very accurate, but it is a "literal" real-time reading, meaning if you bank the aircraft (as in a turn), the distance between the antenna and the aim point on the ground grows longer and so the radar altimeter will indicate a higher than actual height. Likewise with varying terrain (and objects on the ground) as you pass overhead. For example, you might be 200' above the ground, but if you fly over a 2 story building or a big boulder, the radar altimeter will momentarily show you as being "closer" to the ground.

[Eric Hunt]

 

Is there anti-collision technology that reduces the risk of a low-flying chopper from crashing into terrain or landmarks?

How about an electronic altimeter with a warning voice?

How about an auto-pilot function that maintains a preset absolute altitude?

Well, if you are very rich, you could have an F-111 with TFR (Terrain-Following Radar) which maintains your height above the ground as you fly along - it is looking forward, to allow time to fly the machine over obstacles, because you are doing 450 knots plus at 100' agl.

You can select soft, medium or hard ride.

 

But in a helicopter? No. Too expensive, no need for it.

 

How old are you, Jonathan??

[Jonathan Bailey]

Well, if you are very rich, you could have an F-111 with TFR (Terrain-Following Radar) which maintains your height above the ground as you fly along - it is looking forward, to allow time to fly the machine over obstacles, because you are doing 450 knots plus at 100' agl.

You can select soft, medium or hard ride.

 

But in a helicopter? No. Too expensive, no need for it.

 

How old are you, Jonathan??

50, to be exact.

[Wally]

Mr Bailey

It's all situation dependent (safe height above ground, obstructions) and you do it the same way you walk around the house- visually. At least I do/have done so.

Radar altimeters show you what was so a very brief time ago, in the direction it was facing, to the nearest reflective surface returning sufficient signal, and filtered through software to eliminate false positives. I'll set the alert for a significant altitude to provide an aural/visual signal when I pass through that altitude, but I wouldn't set my watch by it much less bet my life on it. I look outside.

Terrain awareness/warning systems usually rely on a position provided by GPS (or whatever), database, and algorithms to trigger various alerts at whatever parameters are written into the program. Useful if you're an airliner, interesting if you're a helicopter. The aircraft I fly now will display terrain from the database on moving map, red, yellow, etc., but that's only useful for planning purposes.

Barometric altimeters of any sort are too slow.

 

There's a huge difference in the visuals from a flight sim and the cues one gets in the real world. I might be comfortable cooking along at 3-10 feet over absolute flat hard packed earth into the wind in some aircraft- visual reference only. No way I'd be as confident in a sim, the subtle visual, proprioceptive, vestibular cues are missing. No gauges or systems I've ever seen would make me comfortable at less than a couple, three hundred feet at the speeds you're talking about.

Me, I cruise at 1500 agl...

Edited March 27, 2014 by Wally

[Jaybee]

I know you said civilian only, but as alluded to above with the F-111.... if you do in fact win the lottery one day you may seek out possible purchase of a PAVE LOW helicopter.....

[Gomer Pylot]

The problem with being concerned only with altitude above the ground is that there are obstacles out there, like towers, powerlines, and other helicopter catchers, and these kill people every year. The minimum safe altitude for the purposes of making an emergency landing after engine failure is in the rotorcraft flight manual (RFM), shown as a height/velocity diagram. The minimum safe altitude for instrumentl flight is shown on instrument charts, and gives 1000' above the highest obstacle. There are other considerations for different flight regimes. In short, there is not a single answer to the question.

[pilot#476398]

What is the minimum safe absolute altitude for a helicopter (flown only for recreational purposes) at a cruising speed say between 110 and 150 knots?

 

 

I ask because my experience in FSX shows that flying low or close to terrain is especially fun and perhaps especially dangerous.

 

Is there anti-collision technology that reduces the risk of a low-flying chopper from crashing into terrain or landmarks?

 

How about an electronic altimeter with a warning voice?

 

How about an auto-pilot function that maintains a preset absolute altitude?

 

One wrong move can cause a captain's ship to run aground.

 

If you are flying recreationally, you most likely won't have any of that high-tech stuff to help you out. Just set you altimeter to the local pressure setting, which will give you your height above sea level. Then look at your chart to determine what altitude you need to fly in order to clear all the obstacles on you route, and fly that altitude because it will be your minimum safe altitude for that trip.

 

If you want to know what absolute altitude that is you'll have to do the math!

 

However, if I were only concerned with engine failure while flying an R44 (a helicopter commonly flown recreationally) at 130kts, my minimum safe absolute altitude would be 20'.

Edited March 28, 2014 by pilot#476398

[aeroscout]

Why don't you fly over water? A radar altimeter is supremely accurate in that instance, as long as you are straight and level, have fairly calm water. And if you fly at a reasonable altitude, you don't have to worry about obstacles, like oil platforms.

[Flying Pig]

My radar altimeter maxes out at 1500'

[aeroscout]

It seems to me all the radalts I have flown max out at 2,500'

[Fliesbecauseracecar]

I can tell you that the one I fly with maxes out at 1500 as well. Although with the correct maps loaded, the aircraft will interpolate AGL altitudes above that as well.