Low Altitude Alert

[Seggy]

Today while coming in on the Expressway Visual to 31 in LGA while turning final, we where told...

"Colgan 4848 low altitude alert altimeter blah blah blah.."

I have gotten this as well going into BOS while on visual approaches. We have been on or above the Glide Slope in visual conditions. One time we where actually above the GS as we where following a 757 and didn't want to hit the wake.

What is the deal with these? What is the proper way for me to respond? Should I say 'roger' or something like 'we are visual'?

[SIUAv8r]

I got one doing a GPS approach. I was always taught to descend to the MDA quickly. I guess I was too low too far out for the tower controller's comfort. I told him I had the altimeter set properly and was at the MDA. I didn't hear another word about it.

[Seggy]

Me thinks it has to do with a 'forecast' of the position of the airplane over a period of time.

What are we suppose to say in regard to one?

[BajtheJino]

I get them all the time on the VOR approach back into my base. I cross the FAF and drop down at about 1000fpm and before hitting mins I get the Low Alt. Alert. I just say thanks and go about my business. I get them too doing the ILS 6 at BHM. Don't know why. As a perfect pilot I'm always on GS.

[SIUAv8r]

Originally Posted by Seggy

Me thinks it has to do with a 'forecast' of the position of the airplane over a period of time.

What are we suppose to say in regard to one?

I'd sure like to know too. I'm not sure how you're supposed to correct for it if , as in your case, you were above the glideslope.

[KC Jake]

Originally Posted by BajtheJino

I get them all the time on the VOR approach back into my base. I cross the FAF and drop down at about 1000fpm and before hitting mins I get the Low Alt. Alert. I just say thanks and go about my business. I get them too doing the ILS 6 at BHM. Don't know why. As a perfect pilot I'm always on GS.

I used to be conceited but now I'm perfect.








Woohoo, 200 posts!

[SIUAv8r]

Originally Posted by BajtheJino

As a perfect pilot I'm always on GS.

Me too

[dc3flyer]

I have gotten a low altitude alert from tower at Hartford on the LDA. It freaked me out, but I just said "Roger" and went on, because I was above the min altitude.

I think it is something that pops up on their screen, and they are required to say something.

[ATC RET 2003]

Here's a chunk from "the book" about it:

2−1−6. SAFETY ALERT
Issue a safety alert to an aircraft if you are aware the
aircraft is in a position/altitude which, in your
judgment, places it in unsafe proximity to terrain,
obstructions, or other aircraft. Once the pilot informs
you action is being taken to resolve the situation, you
may discontinue the issuance of further alerts. Do not
assume that because someone else has responsibility
for the aircraft that the unsafe situation has been
observed and the safety alert issued; inform the
appropriate controller.

NOTE−
1. The issuance of a safety alert is a first priority (see
para2−1−2, Duty Priority) once the controller observes
and recognizes a situation of unsafe aircraft proximity to
terrain, obstacles, or other aircraft. Conditions, such as
workload, traffic volume, the quality/limitations of the
radar system, and the available lead time to react are
factors in determining whether it is reasonable for the
controller to observe and recognize such situations. While
a controller cannot see immediately the development of
every situation where a safety alert must be issued, the
controller must remain vigilant for such situations and
issue a safety alert when the situation is recognized.
2. Recognition of situations of unsafe proximity may result
from MSAW/E−MSAW/LAAS, automatic altitude readouts,
Conflict/Mode C Intruder Alert, observations on a PAR
scope, or pilot reports.
3. Once the alert is issued, it is solely the pilot’s
prerogative to determine what course of action, if any, will
be taken.

a. Terrain/Obstruction Alert. Immediately issue/
initiate an alert to an aircraft if you are aware the
aircraft is at an altitude which, in your judgment,
places it in unsafe proximity to terrain/obstructions.

Issue the alert as follows:
PHRASEOLOGY−
LOW ALTITUDE ALERT (call sign),
CHECK YOUR ALTITUDE IMMEDIATELY.
THE (as appropriate) MEA/MVA/MOCA/MIA IN YOUR
AREA IS (altitude),
or if an aircraft is past the final approach fix
(nonprecision approach),
or the outer marker,
or the fix used in lieu of the outer marker (precision
approach),
and, if known, issue
THE (as appropriate) MDA/DH IS (altitude).


If I was working you from the tower and got an alarm, I'd usually have a look out the window and, unless you were in an unusual attitude for your phase of flight or were coming down like a sack of hammers, I probably wouldn't say anything.

If I was in the radar room, since there's no way to see out, I'd probably issue the alert. Even though you are on a visual approach, it's a tough sell to explain why no alert was issued if, heaven forbid, something happened.

As far as how you should reply when an alert is issued... "roger" always worked just fine for me.

[SIUAv8r]

Thanks for the response!

[Ian J]

Originally Posted by dc3flyer

I have gotten a low altitude alert from tower at Hartford on the LDA. It freaked me out, but I just said "Roger" and went on, because I was above the min altitude.

I think it is something that pops up on their screen, and they are required to say something.

I get these on the HFD LDA all the time, too. I asked the tower controller and he gave me a pretty in depth explanation on how their system works. Basically, the computer calculates your decent rate and projects where you will be in X amount of time. If in X amount of time it thinks you will smack the ground it issues an alert and the controller has to warn you.

When I get the alerts, I just respond with my altitude.

[Fox Xray]

I'm not familiar with the radar used by approach (Micro EARTS ?) but in the center environment we use DSR which has an MSAW (Minimum Safe Altitude Warning) alert that flashes on the screen.

Sometimes after we hand A/C off to approach we'll get an alert and generally it's triggered by the A/C descending rapidly. Just like our conflict alert it's my understanding that the MSAW alert uses "predictive" information to trigger the alert.

Most likely you're seeing something like this happening.

[Ozelot]

At the facility I used to work at, an MSAW alert only happened when an aircraft was within a few miles from the runway or when we cleared a pilot for a visual approach and they would get lower then the MVA farther from the airport. My trainers always told me that when they are cleared for a visual approach its their own responsibility to keep from hitting obstructions and terrain. So the only time I've ever used the phraseology was in training cause we always got ripped on for saying it to A/C on a visual approach.

[Towerboss]

Fox Xray at the TRACON I work at we use ASR-9 (Airport Surveillance Radar System model 9)

It has MSAW and yes it is a "predictive" system.

I agree and what I do is the same as ATC RET 2003.

[ATC RET 2003]

Originally Posted by Towerboss

...and what I do is the same as ATC RET 2003.

I always liked you and I have NEVER messed with Texas.

[Towerboss]

Originally Posted by ATC RET 2003

I always liked you and I have NEVER messed with Texas.

LOL

TB

[Elfmaze]

We have to give low altitude alerts all the time. When we are using our loc bc mostly. But if the celing is at 800Ft or so the aircraft will dive below the clouds four miles out. The computer predicts that at that current decent rate the aircraft will not make the airport and "lala's" at us. We also get a call from the tracon. It is mandatory for us to tell the aircraft that they are getting an alert and tell them the minimum decent for the approach.

[ATLTRACON]

All airspace is sorted into "sort boxes" that have a MSA/MVA built into it. If our computers show a high rate of decent or that you are below the MSA/MVA, even though you are on a visual approach, the low altitude alert is going to go off on our scopes and we are required to say something.

Happens about 100+ times a day at PDK if they are on 2R. The antennas south of the field trigger it.