Call a "cat" a "cat" - Altitude vs height vs AGL vs MSL ...

[Crusader14]

Might depend on country....

In the UK it helps to think of the drone being in the middle of a 400ft bubble. the edge of the bubble must always touch something.

That’s not quite accurate. The edge of the bubble must always touch the ground.

 

[Crusader14]

Altitude vs height
- - - I can fly at 400 feet maximum altitude, but I can legally exceed that by 400 feet more when I fly over a tower of 700 feet height!

So, for me I mostly interpret height as distance of measure from the ground to top of an object, whereas I interpret altitude as the distance between the ground to an object suspended in air above or below my level of the ground. The cliff I am on is 1000 feet high and my drone flies off and down, I am still ar 1000 feet height but the drone now gains negative altitude.

My 2 cents only, not trying to establish definitions, but rather how I use them.

No you can’t fly over a 700ft obstacle at 400ft because that will place you 1100ft above the ground. 400ft AGL MAX.

 

[sar104]

No you can’t fly over a 700ft obstacle at 400ft because that will place you 1100ft above the ground. 400ft AGL MAX.

It depends where you are and which rules you are flying under. In the US, under Part 107, that is permitted. See post #25 above.

 

[Crusader14]

It depends where you are and which rules you are flying under. In the US, under Part 107, that is permitted. See post #25 above.

That’s fair. I was referring to the U.K.

 

[sar104]

That’s fair. I was referring to the U.K.

I guessed that you probably were, but you were responding to someone in the US so I thought it was worth a clarification.

 

[Crusader14]

The legal requirement is the height limit AGL. From Section 349 (recreational exemption):

49 USC 44809: Exception for limited recreational operations of unmanned aircraft​

​

(a) (6) In Class G airspace, the aircraft is flown from the​

surface to not more than 400 feet above ground level and complies​

with all airspace restrictions and prohibitions.​

From Part 107 (non-recreational flights):

§107.51: Operating limitations for small unmanned aircraft.​

A remote pilot in command and the person manipulating the flight controls of the small unmanned aircraft system must comply with all of the following operating limitations when operating a small unmanned aircraft system:​

​

(a) The groundspeed of the small unmanned aircraft may not exceed 87 knots (100 miles per hour).​

​

(b) The altitude of the small unmanned aircraft cannot be higher than 400 feet above ground level, unless the small unmanned aircraft:​

​

(1) Is flown within a 400-foot radius of a structure; and​

​

(2) Does not fly higher than 400 feet above the structure's immediate uppermost limit.​

​

(c) The minimum flight visibility, as observed from the location of the control station must be no less than 3 statute miles. For purposes of this section, flight visibility means the average slant distance from the control station at which prominent unlighted objects may be seen and identified by day and prominent lighted objects may be seen and identified by night.​

​

(d) The minimum distance of the small unmanned aircraft from clouds must be no less than:​

​

(1) 500 feet below the cloud; and​

​

(2) 2,000 feet horizontally from the cloud.​

Interesting. This means that in the US it would appear that maximum height is not 400ft AGL but 400 ft MSD that is Minimum Separation Distance. In other words as I understand it, in the US the maximum height you can fly your drone is 400ft above the obstacle over which you are flying. This could mean that drones can legally fly many many hundreds of feet above the ground to stay 400ft clear of obstacles?

 

[sar104]

Interesting. This means that in the US it would appear that maximum height is not 400ft AGL but 400 ft MSD that is Minimum Separation Distance. In other words as I understand it, in the US the maximum height you can fly your drone is 400ft above the obstacle over which you are flying. This could mean that drones can legally fly many many hundreds of feet above the ground to stay 400ft clear of obstacles?

Under Part 107, provided that you are within 400 ft laterally of the obstacle - yes.

 

[Andy Mac 230]

Crusader I like it and smack on! Just don’t lift the lid off the QFE/QNH debate for approaches to a military airfield in a civilian aircraft!!
Are you ex military per chance I only ask because you are knowledgeable about the Q code and QFE is definitely a military thing?

 

[Andy Mac 230]

Sandy Heath transmitting station - Wikipedia

en.wikipedia.org

So if we applied FAA we would be at1200 feet AGL to clear this little baby (801ft tall)

 

[Andy Mac 230]

Just reread 107 isn’t that ruling for commercial operators
“For non recreational operators”?

 

[AnzacJack]

Then of course you can throw in pressure height and density height ?

(only mentioned as I’m teaching this at the moment - only used in performance calculations)

 

[Andy Mac 230]

8/10 for stirring it.....see me!!

 

[Andy Mac 230]

Never mind temperature fluctuation etc etc..
it’s called Zymurphies Law......
if you take the lid off a can of worms....you will never get them all back in.

 

[sar104]

Sandy Heath transmitting station - Wikipedia

en.wikipedia.org

So if we applied FAA we would be at1200 feet AGL to clear this little baby (801ft tall)

Correct.

Just reread 107 isn’t that ruling for commercial operators
“For non recreational operators”?

Yes - I pointed that out several times. Part 107 flights can be recreational or non-recreational.

 

[Andy Mac 230]

So does the 400 ft MSD rule apply to both types of operator. It’s just as I read it commercial operators have the dispensation but not Pleasure operators. I’m glad to see the FAA and CAA have the same use of grey rulings lol...or am I just being a bit Derrr! Lol

 

[Andy Mac 230]

My interpretation is the same as Crusader but that’s because we are used to CAA regs

 

[sar104]

So does the 400 ft MSD rule apply to both types of operator. It’s just as I read it commercial operators have the dispensation but not Pleasure operators. I’m glad to see the FAA and CAA have the same use of grey rulings lol...or am I just being a bit Derrr! Lol

You are confusing class of operator with class of flight. A Part 107 certified pilot can fly recreationally or non-recreationally under Part 107 regulations. Without a Part 107 certification you can only fly recreationally, under the "Exception for limited recreational operations of unmanned aircraft" - Sec. 44809.

 

[Andy Mac 230]

Yep I understand that but as I read in only part 107 pilots whether flying commercially or for pleasure can apply the 400 ft MSD Applying the supposed increase in knowledge and experience. Which as I read the non 107 licenced guys cannot apply the dispensation and are limited to 400 feet AGL so would therefore have to fly around the obstacle??

 

[Andy Mac 230]

Still I know our rules and as a non commercial pilot I will stick to them..and to think we nearly had EU rules thrown in to the mix

 

[sar104]

Yep I understand that but as I read in only part 107 pilots whether flying commercially or for pleasure can apply the 400 ft MSD Applying the supposed increase in knowledge and experience. Which as I read the non 107 licenced guys cannot apply the dispensation and are limited to 400 feet AGL so would therefore have to fly around the obstacle??

That's correct.