Paul Holmes and Erebus

[compressor stall]

Amman, most ASPAs (well the ones I have had to avoid) have a minimum altitude of 2500 feet overflight to protect the wildlife. I'll check for Cape Hallet, but suspect it would be no different.

[compressor stall]

http://www.ats.aq/documents/recatt/Att443_e.pdf

Only 2000 feet...

[prospector]

I suggest it's common sense that before beginning a VMC descent in a mountainous area, without any ground aids available, you first visually identifiy the mountain(s) itself. To me that just seems intuitively basic to any philosophy espousing "fail safe flying."

And that would be a very valid suggestion that I for one would agree with wholeheartedly.

[prospector]

Compressor stall,

Could you please give your opinion on the validity of the requirement to remain above 6,000ft, using the possibility of bird strike with skua gulls as one of the reasons???

[ampan]

Compressor Stall: Thanks for the clarification. I'm sure the little penguins could handle a DC10 that's 33000 feet away.

Prospector: I vaguely recall reading something about skua gulls and height limits. They're definitely big birds. (The other large flying bird in the region is a species of albatross, but they tend to fly low, using ground effect.)

[compressor stall]

In my experience, I don't recall seen a skua in flight from the air in the cruise below 10K, and I've flown along ~1/3 of the Antarctic coastline at 6000 feet or below. (On low level survey, however, <1000' I've seen a lot of birds including skuas, but that's irrelevant to the discussion).

I'm not comfortable criticising any risk analysis regarding altitudes for skua avoidance around the McMurdo area, especially as I've only flown into and out of the Ross Sea area to/from flight levels.

Having said all that, it's all a matter of likelihood and consequence. I believe that chances of a QF/DJ 737 hitting a small "fire hawk" (similar sized bird) in outback Australia would be at least one order of magnitude higher. However a buggered engine in Kalgoorlie is not as much of an issue as a buggered engine at 78S.

[prospector]

compressor stall,

Thanks, do you still have that photo approaching McMurdo Sound taken from the flight levels? as I recall it showed Ross Island, Mt Erebus and Beaufort Island to perfection. It showed the likely difference in weather conditions that previous flights had for a VMC descent as against the conditions that were prevailing for Capt Collins flight.

[compressor stall]

I can't find it at the moment on my photobucket site. In the mean time, have this one to ponder whilst I stitch the images together again.

[ampan]

That's two big hailstorms and a smaller one - or two big mountains covered in hail and a smaller one, otherwise known as Ross Island.

[chris lz]

Originally Posted by ampan

Chris Iz - They checked the black box to see what happened at Cape Hallett. This is from MB Wylie, an NZ government accident inspector:

Thanks - I've only looked at the Chippindale report proper and don't recall seeing this.

Originally Posted by FGD135

You don't even need to know your position - you can be totally lost!

That's what I used to think until I encountered commercial pilots on internet forums. How many do you think would agree with you?

[prospector]

Hope that is not a Bendix radar, they will not show up Ross Is, despite what a number of crews said to the contrary.

[ampan]

Chris Iz: I wouldn't disagree with FGD135. The best description I've read was on the other Erebus thread, by someone with the moniker of Bryan Abraham, who used the phrase "VMC bubble". This was another of those VMC/IFC accidents, just like JFK Jnr. He thought he could follow the lights along the coast to Martha's Vineyard, but couldn't see the cloud ahead, because it was dark. Once he entered the cloud, he lost all visual reference and couldn't distinguish up from down. If he had bothered to get his instrument rating, it would have been drummed into his head that he was to ignore his eyes and fly solely on his instruments.

[prospector]

It is not necessary to see and identify ground obstacles before switching to visual flight, but you must be in VMC at that point (in order to see that you can continue in VMC). You don't even need to know your position - you can be totally lost!

I would not agree with that statement. You are either on a VFR plan or an IFR plan, you certainly would not be flying IMC without being on an IFR plan. If you are on an IFR plan then the controllers must provide separation, either vertical or horizontal, from traffic, and terrain, by using MSA (Minimum Safe Altitude) When you request VMC then you must be coming from an IFR plan, you are then responisble for your own terrain and traffic separation. If you are responsible for your own terrain separation then you must know where that terrain is relative to your position., How could this happen if you were lost???



If you are on an IFR plan you would be flying, normally, on a track from beacon to beacon, or with modern gear, GPS, direct to your destination.

If you wanted then to proceed VMC, weather permitting, which is normally requested for a descent to destination you could request a VMC descent. This to save the round about way of descent via an Instrument Approach Procedure. If, after requesting VMC flight, you do not wish to proceed directly to your planned destination then you must advise the controller, .cancel your IFR plan and proceed VFR.

Or that's the way it used to be.

[FGD135]

I would not agree with that statement.

My statement was related to the simplest set of circumstances. To bring in ATC, clearances and flight plans is unnecessarily complicating things.

There is no law or rule that I know of that says you must know your position before switching to visual navigation. Similarly, there is no law for the reverse situation (switching from visual navigation).

Note that we are not talking about switching from IFR to VFR. The aircraft can still be following IFR procedures whilst navigating visually.

That's what I used to think until I encountered commercial pilots on internet forums. How many do you think would agree with you?

If they don't agree then I would suggest the reason was that they misunderstand the question. Go back to those forums and ask specifically:

Is it a requirement that an IFR aircraft that is switching from navaid/RNAV navigation methods to visual navigation must know its position before making the switch?

My statements in this area have been to address an apparent belief held by chris lz that a pilot must be certain of his position before switching to visual navigation.

There is also no law against being lost or uncertain of position!

[chris lz]

Originally Posted by FGD135

My statements in this area have been to address an apparent belief held by chris lz that a pilot must be certain of his position before switching to visual navigation.

Thanks. This is precisely the kind of nuance that's key to one's understanding. Maybe my assumption is incorrect. Let's be very specific: to other pilots still tuning in:

1) is there a formal rule that states when switching from instrument flying to VMC you must first establish your position with (a high degree of) certainty?

2) If not, is the argument then that "certainty of position" is implied by any standard of responsible airmanship while VMC - at least with 300 pax behind you?

My thinking has been that either 1) or 2) must be correct.

Pilots: speak

Thank you

[prospector]

My statement was related to the simplest set of circumstances. To bring in ATC, clearances and flight plans is unnecessarily complicating things.

Sorry, but that is what happens in the real world.

[FGD135]

Sorry, but that is what happens in the real world.

Agreed!

chris lz, answers:

1) No
2) Yes

Note that an IFR aircraft may be navigated by visual means, if desired. The aircraft is still effectively IFR.

Similarly, a VFR aircraft may be navigated entirely via means normally utilised by IFR flights (e.g, using ground-based navaids such as VOR, NDB, DME or RNAV-based systems such as INS, GPS, LORAN, etc).

TE901 was being navigated visually, but was still operating to the IFR.

This is quite different from an aircraft that has switched from IFR to VFR. A VFR aircraft must conform to strict rules regarding visibility and separation from cloud, whereas an IFR aircraft navigating visually is not bound to those VMC requirements.

[FGD135]

An absolutely striking image of Mt Erebus, Mt Terror and Mt Bird, thanks stallie!

Mt Erebus gets all the attention but to help appreciate the terrain of Ross Island, it is worth remembering that Mt Bird - the smaller of the three blobs - is itself almost 6,000' above sea level!

Hope that is not a Bendix radar, they will not show up Ross Is, despite what a number of crews said to the contrary.

That image could not have come from any radar because it shows the mountains as circular shapes. A radar would only be able to see the sides facing the aircraft.

That image is from the EGPWS (Enhanced Ground Proximity Warning System), which has been regular equipment in airliners for only about the last 15 years.

[DozyWannabe]

Originally Posted by FGD135

At the point where Collins realised he didn't have adequate visual reference it was too late for any escape.

Or to be more precise, lost the visual references he thought he had up until that point.

[chris lz]

Originally Posted by FGD135

Agreed!

chris lz, answers:

1) No
2) Yes

In regard to 2) above, just curious how this strikes you:


- The crew's reliance on AINS resulted in plane hitting mountain

- The crew's reliance on ground aids would not have resulted in plane hitting mountain

-It follows that reliance on AINS is not a substitute for ground aids.


Evaluate.