XXXX10
Topic Author
Posts: 702
Joined: Mon Jan 03, 2000 7:10 am

MSA

Sat Apr 20, 2002 10:57 pm

Can anyone tell me how minimum Safety Altitude is decided.

It doesn,t seem to relate to the height of the terian?

Many thanks
 
JETPILOT
Posts: 3094
Joined: Tue May 18, 1999 6:40 am

RE: MSA

Sun Apr 21, 2002 1:01 am

I havent used a VFR sectional for about a decade but I seem to remeber it being 1000? feet above the highest obstacle in the sector.

JET
 
DG_pilot
Posts: 810
Joined: Tue Sep 07, 1999 10:21 am

RE: MSA

Sun Apr 21, 2002 4:43 am

Isn't there a MSA on approach plates as well?
 
Guest

RE: MSA

Sun Apr 21, 2002 5:55 am


MSA, or Minimum Safe Altitude, provides 1000 feet of obstacle clearance, within 25 NM of the navigational station indicated on the approach plate. For example, right now, I'm looking at the ILS Rwy 24 Approach to Martha's Vinyard, Massachusetts. The MSA part says "MSA MVY 25 NM" Meaning that the MSA is determined in terms of distance from the MVY VOR. And there are different sectors with different altitudes defined by radials from the VOR.

MSA does not provide for navigation or communcation signal reception, only obstacle clearance. It is only for use in emergencies or VFR flight. And, the MSA shown on the approach plate is only valid for that approach. Other MSAs apply to other approaches. And, not every approach has an MSA.

'Speed
 
ThirtyEcho
Posts: 1409
Joined: Tue Jan 01, 2002 1:21 am

RE: MSA

Sun Apr 21, 2002 9:42 am

Actually, it is "Minimum Sector Altitude" unless something changed recently. When all else fails, including the missed approach procedure, go to the MSA.
 
ThirtyEcho
Posts: 1409
Joined: Tue Jan 01, 2002 1:21 am

RE: MSA

Sun Apr 21, 2002 10:06 am

Wait...Of course it is "Minimum Safe Altitude." The altitudes depicted on sectionals are "Minimum Sector Altitude." Sorry.
 
Guest

RE: MSA

Sun Apr 21, 2002 10:06 am

Actually, it is "Minimum Sector Altitude" unless something changed recently.

I did a little digging, and this is what I came up with:

In the Abreviations section of my Jepp Airway Manual, MSA is "Minimum Safe Altitude." The same goes for the Pilot/Controller Glossary in the AIM. But, in the AIM section 5-4-5, MSA is written, "Minimum Safe/Sector Altitude." And, the term "MSA" isn't mentioned in FAR part 1. So I suppose that either "safe" or "sector" is acceptable. But if it's alright with you, I think I'm going to keep on saying "safe."

Here's the VFR meaning of MSA:

Anywhere: An altitude allowing an emergency landing without undue hazard to people or objects on the ground.

Over Congested Areas: At least 1000 feet above any object with in a 2000 ft radius of the aircraft.

Over Non-Congested Areas: No closer than 500 feet to any object or person on the surface.

Hope this helps,

'Speed

 
JETPILOT
Posts: 3094
Joined: Tue May 18, 1999 6:40 am

RE: MSA

Sun Apr 21, 2002 4:47 pm

Unless I'm mistaken and I'm sure someone will point it out.....

I've been briefing approach plates for about 8 years now..... I thought MSA on an approach plate was minimum safe altitude, at least thats what I've been calling it.

I thought minimum sector altitude was the large numbers on each sector on a sectional chart indicating the altitude which will give you 1000 feet obstacle clearance in that sector.

?????

JET
 
Guest

RE: MSA

Mon Apr 22, 2002 12:01 am

I thought minimum sector altitude was the large numbers on each sector on a sectional chart indicating the altitude which will give you 1000 feet obstacle clearance in that sector.

On a Sectional Chart, that figure is called an "MEF" or Maximum Elevation Figure. This represents the highest known terrain or obstruction (the NOS calls these "features") in the quadrangle, and does not provide obstacle clearance.

IFR Low Altitude enroute charts also have similar figures. Jepp calls it a "MORA" (Minimum Of Route Altitude) and, the NOS calls it an "OROCA" (Off Route Obstacle Clearance Altitude). The OROCA and MORA provide 1000 feet of obstacle clearance in non-mountainous terrain (below 7000' MSL), and 2000 feet of obstacle clearance in mountainous terrain (above 7000' MSL). Also, Jepp prints the MORA figures that are above 14000' MSL in red, suggesting the use of oxygen, and the figures below 14000' MSL in green.

And, IFR High Altitude enroute charts have no such figures - they aren't needed, since their MEAs, unless stated at a higher altitude, are FL180.

'Speed
 
JETPILOT
Posts: 3094
Joined: Tue May 18, 1999 6:40 am

RE: MSA

Mon Apr 22, 2002 7:09 am

Thanks for clearing that up...... I remeber MEF now.....

Thanks

JET
 
Guest

RE: MSA

Mon Apr 22, 2002 8:18 am

On a Sectional Chart, that figure is called an "MEF" or Maximum Elevation Figure. This represents the highest known terrain or obstruction (the NOS calls these "features") in the quadrangle, and does not provide obstacle clearance.

Turns out that what I wrote here isn't quite accurate. MEFs do provide a small amount of obstacle clearance. MEFs are rounded up to the nearest 100 feet, and then adjusted upward 100 to 300 feet, depending on the type of obstacle.

'Speed

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