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Bombardier 605 crash yesterday.

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Bombardier 605 crash yesterday.

Old 30th Jul 2021, 12:07
  #21 (permalink)  
 
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A review of the first post of the approach plate shows that a circling procedure is not authorized at this airport in Category D.
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Old 30th Jul 2021, 12:37
  #22 (permalink)  
 
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I agree with Charlie Foxtrot. Absolutely. Starting high and fast and the IAF for a "not so simple" approach had "go-around" written all over it and compressed the situation beyond normal limits. Perhaps the PIC had no previous experience at that airport. I would venture to say it is likely he was tankering enough fuel for the next flight. He also had the highest airport temperature at that time. Not even sure who the SIC was but this morning the PIC was identified along with the passengers on board. Any accident is bad enough but this was just tragic from the start.
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Old 30th Jul 2021, 18:59
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Originally Posted by BizJetJock View Post
Er... yes it is. This is a TERPS approach in the USA, max IAS for circling in Cat C is 140kts. Min speed for circling in a Challenger is 150 kts, so it is Cat D.

So they should not have been even considerin a circling approach.
I was not aware of a min circling speed.
A quick glance does not list it in the Limitations section. I have no experience in the airplane type. Do you have a reference?
Requesting the approach for 11 could have avoided the problem.
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Old 30th Jul 2021, 20:25
  #24 (permalink)  
 
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The SmartCockpit site Challenger 605 circling approach diagram says says circling approach at the start of downwind Flaps 30 and speed Flaps 30 speed + 10 KIAS.

What was their weight and what is the corresponding flaps 30 speed? I haven't found that yet.
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Old 31st Jul 2021, 00:02
  #25 (permalink)  
 
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Originally Posted by Raffles S.A. View Post
The SmartCockpit site Challenger 605 circling approach diagram says says circling approach at the start of downwind Flaps 30 and speed Flaps 30 speed + 10 KIAS.

What was their weight and what is the corresponding flaps 30 speed? I haven't found that yet.
Regardless of whatever the speed was, it's still Cat D.

MS
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Old 31st Jul 2021, 00:45
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The FAA recently published revisions to the Aeronautical Information Manual (AIM), including clarifications of “approach category” and its application in determining the appropriate straight-in or circling minima on an instrument approach.

Previous AIM language required pilots to use the next higher approach category if it was necessary to maneuver at a speed above the upper limits of the aircraft’s defined approach category.

The revised language advises a pilot is never required to use the next higher approach category.
https://nbaa.org/aircraft-operations...ed-procedures/
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Old 1st Aug 2021, 15:04
  #27 (permalink)  
 
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B2N2

The more significant quote from that NBAA advice would have been
In order to remain in protected airspace, it is still recommended – but no longer required – that pilots use the next higher approach category if possible, Boll explained.
In other words, the obstacles don't care if a jet is certified as Cat C or D.

If a pilot needs to circle at speeds above 140 KIAS for whatever reason - configuration, icing, a jammed stab, turbulence, whatever - s/he would be wise to respect the Cat D line of minima.
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Old 2nd Aug 2021, 03:11
  #28 (permalink)  
 
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Cat D?

Originally Posted by BizJetJock View Post
Er... yes it is. This is a TERPS approach in the USA, max IAS for circling in Cat C is 140kts. Min speed for circling in a Challenger is 150 kts, so it is Cat D.

So they should not have been even considerin a circling approach.


FSIMS.FAA.GOV States Cat C for the 604 & 605 ?
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Old 2nd Aug 2021, 04:36
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comments are pretty good
but nobody really knows why yet
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Old 2nd Aug 2021, 05:53
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I have never encountered "FU" conditions, but I understand that smoke haze significantly affected viz at the time of the crash despite a theoretical good viz.

I have flown into Truckee as pax looking over the crews' shoulders in a Citation X, straight in, downwind onto 11. It's tight, hot and high. I struggle to imagine a "circling approach" in such an aircraft. It does look a lot like a typical general aviation overshoot-stall -spin, I wonder if misleading visual cues due to smoke contributed.

Last edited by double_barrel; 2nd Aug 2021 at 06:09.
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Old 2nd Aug 2021, 11:34
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Let’s clarify a couple of things:

1. An airplane is assigned an approach category based on its Vref at max landing weight. Lack thereof it’s Vso x 1.3
2. If the approach speed is lower due to lower actual landing weight the Category does not change as in “we’re light today so we use the Cat C minima”.
3. If the approach speed is higher for whatever reason ( configuration issues or malfunctions)it is prudent to use the higher Category minima and restrictions.

Which leads to the following:
It is not illegal for a Cat C aircraft to fly a higher speed even though Cat D is Not Authorized.
The approach is not authorized for Cat D (large) aircraft that’s all that means.

Now it would be prudent to take note of the restrictions or limitations on the Approach plate………
If we find ourselves in a situation where we have to fly a higher speed.
This would be a highlight item during a approach briefing in the cockpit.

I’m still curious why they choose to fly the approach that required circling instead of the offset approach to RWY 11.


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Old 2nd Aug 2021, 13:19
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Why Rwy 11 … or Rwy 29?

The ATC audio identities the controller offering the pilot either Rwy 11 or overhead downwind 29… pilots choice. Metar 30 mins prior to arrival posted on this website would have favored Rwy 11. 30 mins after the accident, Metar would have preferred Rwy 29. KTRK is tight and unforgiving sad to say…3 1/2sm FU. 3sm needed to circle Cat C. One would have to be on the RNAV 20 at YAKYU (2.6 from MAP and 3.2 from the airport) no less than 7200ft and circle inside an obstacle at 6817ft on the extended Rwy 11 centerline - not easy even at Ref + 10 …if the wind had already shifted to the west over the surrounding terrain and not known (or requested) prior to the commencement of the circle… … a difficult challenge for even the best skills.. if the MAP is reached at only 0.8 from the field, circling for 11 would be unlikely. It appears that the flight track was west of the RNAV 20 approach (even west of I-80) suggesting a visual approach was occurring inside of LUMMO.

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Old 2nd Aug 2021, 15:55
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Some real numbers for one of the 605s I fly:
Operating weight with 2 pilots - 27,151lbs
Zero fuel weight with 4 pax and some bags - 28,250lbs
Absolute minimum fuel for flight planned arrival - 2,000lbs. Most pilots are comfortable with 3k+, and they could have been tankering, but this gives us the lowest speeds.

Vref for 30,250lbs at 4500ft elevation - 121kts
For a more likely 32,000 - 126kts
The FCOM says that circling should be done at the Flaps30 speed +10kts. Unfortunately, nowhere is the Flaps30 speed defined. If you take it as being the speed you get from the FLAPS FAIL checklist at Flaps 30, then you get speeds of 138 and 143 respectively. Most operators fly as they have been trained by CAE and FSI and use 150 unless the weight requires more.
So it is theoretically possible to get below 140 if they were light enough, but in practice not likely.
I hadn't spotted the AIM change. They have changed "must" use the higher category minima to "should". In my book, "should" suggests you need quite a good reason not to, and the Boss wanting to get to his summer home doesn't seem good enough, particulary given that even the Cat D protecterd area is quite tight to do any kind of sensible circuit. Everyone who has done the JFK and Memphis circles in the Challenger sim knows that it is rarely a stable approach in anyone's book!
Obviously we need to wait for some facts, but sadly i think that this will demonstrate that pushing things to the limit just because it is legal doesn't mean it is a good idea.
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Old 2nd Aug 2021, 16:52
  #34 (permalink)  
 
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Originally Posted by BizJetJock View Post
Obviously we need to wait for some facts, but sadly i think that this will demonstrate that pushing things to the limit just because it is legal doesn't mean it is a good idea.
Like button ^^^
Barely legal is rarely a good idea.
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Old 3rd Aug 2021, 02:38
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Question: From what I know the A/C category is determined using the Vref and not the specific speed flown in a circling approach. Correct?
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Old 3rd Aug 2021, 07:52
  #36 (permalink)  
 
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Originally Posted by EDML View Post
Question: From what I know the A/C category is determined using the Vref and not the specific speed flown in a circling approach. Correct?
The simple answer to that would be, yes. Just note that for the certification of the aircraft and when determining the aircraft category, the Vref on a straight-in approach and landing (not a circling approach (turning)) at Aircraft Max Landing Weight is used.
Since the circling approach requires banking (turning) during the maneuvering to land, the aircraft speed needs to be increased (above Vref) to increase the safety margin. The pilot will therefor need to use a speed with an increment during the circling approach, and depending on aircraft performance and operational procedures (Manufacturer or Operator), this speed may be higher than the MAX maneuvering speed depicted (for that aircraft performance category) on the approach chart. Accordingly, the operator may decide to perform the approach in a higher aircraft category (in the case of this accident Cat D) and using the minima's and performance criteria (such as circling protection area etc.) associated with that higher category.
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Old 5th Aug 2021, 17:06
  #37 (permalink)  
 
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B2N,

I politely have a different view to you about approach categories. My understanding is that the pilot should fly the category procedure for the speeds being flown at the particular point in the arrival and approach, they vary during the different segments of the arrival and are speed brackets both in PanOps and TERPS. The categories have a maximum and minimum speed for each category at that point in the approach, you fly the category for the speed you are flying.
The information is available in Jepp etc but can also be found here Aircraft Approach Categories. The category as determined by the Vref at the time it is flown is used to ascertain the approach minima. The other sector categories must be determined according to the speeds flown at the time because the obstacle clearance is related to turn radius at the speed being flown and also visibility are calculated in accordance to the speed being flown.

MM
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Old 5th Aug 2021, 19:21
  #38 (permalink)  
 
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MM, respectfully I don’t think we’re disagreeing on the core of the issue. We’re just getting there through different avenues.
The aircraft is Cat C so it is legal to fly the circling approach.
Cat D are not authorized to circle even if they are light and use a Cat C speed.
The aircraft is still Cat D and therefore prohibited.
Now….a crew flying said Cat C aircraft are legal to fly a higher speed and it would be prudent to use the higher Cat D minima.
Which in this case would indicate they should not accept the circling approach as cleared by ATC.
Vref is Vref by its definition, it’s not a stall speed. One knot below Vref does not mean instant doom and neither does a standard rate turn at Vref.

Now from the discussion here it appears normal circling speed for the 605 is 150kts which means the crew should have used the Cat D minima and at the lack thereof………
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Old 6th Aug 2021, 06:16
  #39 (permalink)  
 
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Old 6th Aug 2021, 10:06
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Originally Posted by 340drvr View Post
Audio of the plane and ATC shows they were indeed going for the Rwy 20 approach - circle to rwy 11.
Conditions at the time were pretty marginal for circle-to-land, smoke, storms in the area:
METARs at approx. time (2018Z) of crash:

KTRK 262050Z AUTO 28011G16KT 04SM BKN023 33/08 A3013 FU RMK VIS 3 1/2/V5 FU BKN023 ACFT MSHP
KTRK 261945Z AUTO 09005KT 04SM BKN023 32/06 A3014 FU RMK VIS 3 1/2/V5 FU BKN023
I would just like make couple of obsevations about the conditions reported in the METARS above ...

Truckee's published airfield elevation is 5904 feet, where the International Standard Atmosphere (ISA) temperature would be 3.306.degrees Celsius, but on the day it was 32 to 33 degrees Celsius. That would make the Density Altitude for those two METARS as 8990 feet and 9149 feet respectively, differing substantially from the physical airfield elevation. Aircraft of any persuasion are going to experience a notable increase in true air speed (TAS) in conditions like this and, therefore, an increased ground speed (GS)

These sort of airfield and meteorological characteristics require careful planning and briefing of the resultant effects of the TAS and GS, allowing more time and track miles (distance over the ground) to get an aircraft safely prepared and configured to fly an approach to landing.

Whilst there are details we have yet to learn about what went on in the cockpit of this accident aircraft, it is pretty much a given that planning for the substantial Density Altitude would need to have been conscientious to lead to a safe outcome.
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