What is the deal with PARs?

[fc2spyguy]

I wasn't disagreeing that Otto knows the definitions, disagreeing that he executed a missed approach at Decision Altitude.

Show me a published "Decision Altitude" for NAS North Whiting Field, and I'll eat crow. However, I demonstrated that there is a published "Decision Height". Yes, DA will EVENTUALLY replace DH - but it hasn't yet. Until that point, he will be executing a missed approach at the DH vice the DA.

Oh, I meant thread split I take no sides, as I still no nothing wrt this. Just working on trimming to neutral and establishing a hover scan . . .

 

[BACONATOR]

Actually based on that context it's clear that the vibrations are being dampened...likely by a dampener. True, there is a secondary definition of dampen to mean to make moist. But, there's also a primary definition of damp which is to affect with a noxious gas. In the example context, both damped and dampened would be correct. There's no reason to suggest otherwise.

I thought the "common use, but still wrong" comment would have cleared this up.

You are arguing context. From a scientific context, to reduce amplitude is to "damp", not dampen. There is a secondary meaning of "dampen" meaning to "dull or deaden" as in to "dampen" one's spirits. That isn't a scientific definiton. Any good dictionary should precede a definition with a context. In the event of "damp", dictionaries will precede it with "physics" or "science" (check it out for yourself). The definition for "dampen" isn't preceded by such a context, meaning it's strictly conversational and non-scientific. From a strictly proper perspective, if you speak to an engineer and say "dampen" instead of "damp", prepare to be corrected.

/nerd

/diction nazi

Ah, but what you're doing in the cockpit has no relation to how the approach was designed. A PAR's or ILS's DH is always based on height above the runway. A PAR controller is telling you you're at decision height when her radar says you're 100 feet above the landing zone...not when you're at some barometric altitude. Same thing goes for an ILS. When these approaches are designed, the basis is AGL.

RNAV approaches are different, because the decision altitude is truly what the aircraft is decending to in MSL. The glideslope indications are being provided by the onboard systems and that's why it's a DA, not a DH.

Ok, you mentioned the PAR, but how does the "design" of an approach factor into a 172 doing an ILS? They don't have RADALTs, so AGL means nothing to them as an indication in the cockpit. You are calling it a "Decision Height", when in fact, the number is actually measured in MSL.

And as for the RNAV, you could argue that GPS-oboard or ILS on deck, a "glideslope" is ALWAYS going to be HEIGHTS determined by a computer for a given angle of approach, whether it's an ILS in the runway or a GPS receiver get signals from above.

 

[BACONATOR]

http://www.merriam-webster.com/dictionary/practicable

They show a synonym being "possible"!!! AHHH! They've forever fucked up my understanding of landing criteria!

So now we only have:

Land immediately

Land as soon as practicable = possible

Land as soon as possible

 

[Gatordev]

Ok, you mentioned the PAR, but how does the "design" of an approach factor into a 172 doing an ILS? They don't have RADALTs, so AGL means nothing to them as an indication in the cockpit. You are calling it a "Decision Height", when in fact, the number is actually measured in MSL.

And as for the RNAV, you could argue that GPS-oboard or ILS on deck, a "glideslope" is ALWAYS going to be HEIGHTS determined by a computer for a given angle of approach, whether it's an ILS in the runway or a GPS receiver get signals from above.

What he's getting at is that when they build the TERPS for the approach, they don't care whether it's a C-150 or a 747. It still has the same glideslope which puts the aircraft at a decision height at a specific point. So as far as the approach is concerned, it's a DH.

I do agree w/ you that as the operator in the aircraft, it's a DA, but that's not the intent of it's use as far as how the approach is built.

 

[Brett327]

I thought the "common use, but still wrong" comment would have cleared this up.

You are arguing context. From a scientific context, to reduce amplitude is to "damp", not dampen. There is a secondary meaning of "dampen" meaning to "dull or deaden" as in to "dampen" one's spirits. That isn't a scientific definiton. Any good dictionary should precede a definition with a context. In the event of "damp", dictionaries will precede it with "physics" or "science" (check it out for yourself). The definition for "dampen" isn't preceded by such a context, meaning it's strictly conversational and non-scientific. From a strictly proper perspective, if you speak to an engineer and say "dampen" instead of "damp", prepare to be corrected.

/nerd

/diction nazi




Ok, you mentioned the PAR, but how does the "design" of an approach factor into a 172 doing an ILS? They don't have RADALTs, so AGL means nothing to them as an indication in the cockpit. You are calling it a "Decision Height", when in fact, the number is actually measured in MSL.

And as for the RNAV, you could argue that GPS-oboard or ILS on deck, a "glideslope" is ALWAYS going to be HEIGHTS determined by a computer for a given angle of approach, whether it's an ILS in the runway or a GPS receiver get signals from above.

I went through this exercise back when I was tuning vibration dampeners - you know, when you were eating lunchables and hiding behind your mother's skirt. BTW, who do you think decided to call them vibration dampeners? Answer: The engineers at Sikorsky :icon_tong There goes your "engineering term" logic. Stop being a brick.

Brett

 

[insanebikerboy]

As hard as is is to write this, I agree with Otto. We execute missed approach at a perscribed altitude (MSL), not height (AGL). In level terrain, the RadAlt can be used as a good backup, but it does not tell us when to execute missed approach. There is nothing in any publication which tells us what our RadAlt will read at the proper missed approach point.

Ah, ok, I see the difference here. Using the radalt is a good BACKUP, but I don't think anyone on here is advocating using the radalt solely as indication of being at DH (except maybe for a CCA/etc/, because the radalt will almost 100% be more accurate than the baralt overwater).

Ok, you mentioned the PAR, but how does the "design" of an approach factor into a 172 doing an ILS? They don't have RADALTs, so AGL means nothing to them as an indication in the cockpit. You are calling it a "Decision Height", when in fact, the number is actually measured in MSL.

The DH's are heights in AGL because the approach is designed to place the aircraft in a position for landing at a specific height above touchdown (hence HAT), not at a specific MSL.

However, the DH's are given in MSL because every aircraft flying instrument approaches are required to have a baralt, not a radalt. That's how the design of the approaches take into account the 172.

 

[a2b2c3]

The DH's are heights in AGL because the approach is designed to place the aircraft in a position for landing at a specific height above touchdown (hence HAT), not at a specific MSL.

Thank you! I was reading through this and hoping to see this. It's a height because it is fixed about a point. At x.x miles you will be at xxx' above touchdown.

 

[Gatordev]

The DH's are heights in AGL because the approach is designed to place the aircraft in a position for landing at a specific height above touchdown (hence HAT), not at a specific MSL.

However, the DH's are given in MSL because every aircraft flying instrument approaches are required to have a baralt, not a radalt. That's how the design of the approaches take into account the 172.

Thank you! I was reading through this and hoping to see this. It's a height because it is fixed about a point. At x.x miles you will be at xxx' above touchdown.

Hmm, this all sounds familiar...

What he's getting at is that when they build the TERPS for the approach, they don't care whether it's a C-150 or a 747. It still has the same glideslope which puts the aircraft at a decision height at a specific point. So as far as the approach is concerned, it's a DH.

I'll blame NMCI lag.

 

[ChunksJR]

It's another instrument in the cockpit that will back you up so use it.

....so....proud...my onwing...<tear>

 

[ChunksJR]

They show a synonym being "possible"!!! AHHH! They've forever fucked up my understanding of landing criteria!

So now we only have:

Land immediately

Land as soon as practicable = possible

Land as soon as possible

Ok...but...

I personally wouldn't be landing on Duck Island (middle of Arabian Gulf) for a land as soon as practicable EP. Just me though...:icon_mi_1

 

[Jim123]

Ok...but...

I personally wouldn't be landing on Duck Island (middle of Arabian Gulf) for a land as soon as practicable EP. Just me though...:icon_mi_1

...land as soon as quackticable?

 

[HuggyU2]

Folks that write NATOPS/Dash-1's don't usually understand what "practicable" means. As we've seen, it doesn't mean "practical".
Example: while it might be practicable to sends kids to school in a hot air balloon, it isn't practical.
Our normal EP phrase is "land as soon as conditions permit". Fortunately, I've seen the word "practicable" removed over the years from flight manuals.

 

[scoolbubba]

Who writes those things, anyways? I understand how changes are submitted, but where did this 1200 page monstrosity with it's own gravity and inertia come from?

 

[teabag53]

While I agree that the NATOPS folks have a somewhat limited command of english they DO have the definition of what the terms mean in the front for those that can't get it.

For the DH v DA debate I think it comes down to standardization and slight technical differences. At the end of the day we all know what DH means and will continue to use it until directed otherwise or a DA is depicted.

While I'm not normally a "it's just been that way so it must stay the same" guy standardized comms are important and minimize confusion during busy times...which is why we don't just make shit up even if it is "more right" when there is already an established convention.

Can't this thread just die???

 

[SkywardET]

So we were coming in recently and the weather was pretty scoch. Low ceilings, rain, fog, all the good stuff. We had planed on a PAR since the ILS glideslope was out. We were coming in for the PAR and Approach told us that the PAR was not working well and we had to do a surveillance approach. Of course we didn't break out. While on missed the weather went below ASR mins, so we were getting ready to go to the alternate. They said something about the PAR not working too well when there are particles in the air. They said they thought they could try it. So we did the PAR and it worked out. No worries.

A couple days later I ran into an ATC guy and asked him about the PAR in rain and such. He said that when there is heavy rain and fog that it can show up on the radar screen and make it difficult to do a PAR approach. He said they have filters and such but they only do so much. So pretty much when the weather is really bad and you need to do a PAR, it don't work.:icon_rage

So my question is if you are going somewhere the only has a PAR for a precision approach and you know the weather is gonna be bad with rain and such, should you just assume the PAR might not work, or do the PARs just suck here?

Every radar is affected by rain and atmospheric conditions. You can turn on all kinds of functions to reduce the effect, such as STC, FTC, and MTI, but it will still be there.

The last school I went to was the FPN-63 PAR. That thing is from the Space Age (read: 1960's). I only learned the technician side, but I could absolutely see it being a beast to work with from the operator side, especially to operate well in extremely adverse conditions. But with all radars, as has been said, it's mostly the operator's game. A new or bad operator can limit the functionality of the radar more than weather.