Tricky IFR Questions At Interviews

[Gateway Customer]

What are some tricky IFR questions that you have been asked in interviews.
It would be nice to hear some questions that people have had trouble with in interviews.

Or on the other hand what are some good questions?

[pistol night]

What are the rules for descending below LSALT at night from FL140 in an unpressurissed, 5 seat, single engine, day VFR category aircraft, carrying 8 passengers, 2 opened cans of Avgas and 3 active fuses of gelignite?

I'm not sure if it's in the AIP's or CAO's. Let me know if you find it:D

[flyby_kiwi]

Are you looking for OZ or NZ IFR interview questions?

[Gateway Customer]

maimly looking for Oz questions, anything would be handy

[The Messiah]

Reaching the minima on the ILS how do you tell if you have 800m, 1.2k or 1.5k vis?

When calculating ROD req'd for a 3 deg slope why do you add the 50'? ie 5 x GS + 50. eg GS 150kt means 800 fpm req'd.

[VH-ABC]

Further to the Messiah's first question...

How do you determine you have the published circling visibility for your catagory of aircraft after an arrival, and how was this number calculated in the first place? No HIAL to help you out with this one.

How about Temperature correction for ILS Glidepath/OM check height for say ISA+20 at 1500'?

Requirements for using Special Alternate wx minimas, including instrumentation AND the other stuff?

[donpizmeov]

I am sorry, but are you going to make a temp correction at ISA+20?

Don

[The Messiah]

Temperature correction at the outer marker, and for ISA +20? come off it!

It is only a gross error check at best anyway and I wouldn't encourage tying yourself up with mental arithmetic at that point during the approach. I accept making a temp correction to the MSA in extreme cold but ISA +20 is not going to cause a problem is it as your true alt would be higher than your altimeter reading.

[VH-ABC]

Messiah,

Agree with yourself and donpizmeof... I wouldnt be sparing much brain bandwidth to calculate out ISA+20 at the outer marker either, however the original thread started by Gateway customer was tricky IFR questions asked in INTERVIEWS.

Good topic too.

[overmars]

my 2 cents worth...

regarding the 50 ft, i am not too sure but it is either because the ILS glideslope is supposed to bring u 50 ft above the threshold, or since its a precision approach, 50 ft has been added for the PEC.

and from night pistol, if its an IFR flight, then if my memory serves me well, you can only descend below the LSALT within the circling area, which for Cat A, is 1.68 nm from the runway threshold. apart from that, the usual requirements: clear of cloud, in sight of runway, min 5 km vis. ref: AIP ENR 1.5

[The Messiah]

overmars

It is neither, and furthermore you don't apply PEC in a 747 yet it is still 5x GS + 50'.

It is in fact basic trigonometry, which would take too long to type here but SOHCAHTOA explains it. Remember that?

[Continental-520]

Overmars,

I reckon PEC is a "one off" 50' amendment.

If we are talking about ROD calculations on a 3deg slope, and if you're adding 50' to the result after 5GS, it would result in a 50 foot per minute increase to your ROD during the approach rather than increasing MDA's, which have no bearing to your ROD calculation.

Me think that the 50' addition to the ROD calculation allows for a more exact profile, i.e. 3.3 degrees.

This of course assuming a fairly typical range of approach ground speeds, for example 120 - 170kts, so CAT B & C, perhaps. If your APP GS is any greater, you may find you have to add more than 50fpm to your ROD calculation to achieve the 3.3 degree slope.

Does this sound feasible or have I had too many jellycups??

520.

[Capt. On Heat]

TCH...............

[VH-ABC]

The maths...

Example 1. G/S 150 kts = 912000 ft/hr (roughly) = 15200 ft/min. That is your horizontal speed.

To achieve 3 degree profile... which is 5 percent... which is 1 in 20, you need 760 ft/min vertical speed.

Or done the quick way, 150 * 5 = 750 fpm.

Example 2. G/S 100 kts = 608000 ft/hr (roughly) = 10133 ft/min.
Again, to achieve 3 degree profile, 5 percent, 1 in 20..., you need 506 ft/min vertical speed.

Or in your head quickly... 100 * 5 = 500 fpm.

Never heard of applying an extra 50 fpm to the calculation, so that's my answer in an interview scenario... and I couldnt fly that accurately if I tried anyway. Gotta use this one as a rough guide for a ballpark figure... I got other things I got to look at in my scan!



Now surely there must be more useful questions that people have been asked in interviews during their careers???

[Pilot steve]

I'm not an IFR driver heres my view of things for those who care

The Maths:
TOA
tan(3)=ROD/GS
tan(3)*GS=ROD (knots)

Theres 1852 m in a nm, and 3.281 ft in a m so nm > ft is *6076.412 and of course hours to minutes is *60.

So converting knots to fpm is 6076/60 = 101.2735

tan(3)*101.2735*GS=ROD
tan(3)*101.2735 = 5.307
So all that crap means that for a 3 degree approach GS*5.307 gives required ROD, so why is 50 ft added? possibly to account for the .307 but then again could be wrong.

My 2c

[Oktas8]

DME gives slant range speed as GS, not 'true' ground speed. So you'd have to use sin not tan if using DME. Not that it makes much difference - I get the same answer as you Pilot steve.

So tell us Messiah - is we right?

[cjam]

I reckon it's probably to make it a tad more accurate. My brain finds it easier to halve my groundspeed then add a zero rather than multiplying by five. Isn't that what most people do? Same result....just seems easier.

[littletruck]

"Keep it simple stupid"

Some good fellow tought me that many moons ago, I still live by it today. I'm with you cjam

[overmars]

I am planning an IFR flight to a destination with an instrument approach chart with the minima titles shaded gray. A colleague of mine told me that if I use the QNH on the aerodrome TAF, I do not have to increase the minima altitudes by 50 ft. Sounds good. But if en route, ATS informs me of the Area QNH, do I use the Area QNH for the approach and increase the minimas by 50 ft, or do I stick to the TAF QNH and leave the minimas as it is?

Hope someone could help me out here.

Thanks.

[ovum]

If you have a local NH you follow the altimeter setting rules and set local NH at the top of descent and leave the minimas as they are. You're only reuired to add 50ft to the minimas if you use the area NH, which you wouldn't do if you have one from the TAF.

The shaded box means nothing unless you have an actual NH - which must be obtained from an ATIS, AWS or AWIS.

...and for those who haven't noticed, a certain key on my keyboard is broken dammit!!

[Oktas8]

So you'd be needing the kyu-NH then...

The letter found on the top left of the keyboard can also be generated by holding the left ALT key down while typing (on the number pad) 0 0 8 1. I'll give it a try: Q. Yup it works.

ASCII code. Whoever would have thought it might come in handy one day?

[The Messiah]

Yeah because using the Tan of 3 deg there is always that bit left over so to allow for it you just add 50.

Just a stupid question from memory and no real importance.

[overmars]

Hi ovum,

So am I right to say that en route, I set my altimeter to the Area QNH and before I start my descent, I set the altimeter to the TAF QNH so that I can disregard the 50 ft increase that will be required if I used the Area QNH?

[fixa24]

i though the 50ft was only added on a precision approach? and only if there was no PEC for your aircraft?
i may be wrong, i'm still studying for IREX...

[overmars]

You are correct there. You add 50 feet to your minima to take into account for PEC if your aircraft manual does not provide for calculations to calculate the PEC.

I am just a bit confused about the Area QNH that is given to by ATS. So, en route, I am supposed to set my altimeter to the Area QNH, and then when I am descending for my approach into the aerodrome, I set the altimeter to the TAF QNH? I would have thought the Area QNH given by ATS would have been more accurate... :hmm:

[Chimbu chuckles]

fixa 24 Add 50' to MDA on a non precision approach.

overmars...no, area QNH is representaive (within 5 mb) of any 'spot' QNH within a defined area. The TAF QNH is valid for various times within the TAF period...for instance if the TAF was a 12 hr one and they gave you 4 QNHs each would be valid for 3 hrs.

[turbantime]

fixa 24 Add 50' to MDA on a non precision approach.

Not true. That 50ft PEC is only applicable to DA's and not MDA's which means precision approaches. You can either use the aircraft's flight manual to figure out pressure error or use the 50ft addition as an alternative.

Jepp Terminal 2.6.2 Compensation for aircraft pressure error is not required when determining AOM (aerodrome operating minima) for non-precision approaches.

I would have thought the Area QNH given by ATS would have been more accurate

In addition to chimbu's response above, the area QNH given by ATC is also a forecast. There have been many a time when an area QNH delivered to me has been quite different to a/d QNH and when I questioned it, they have gone to the Sydney ADI or closest controlled aerodrome's ADI and passed that QNH on to me (mind you, I was transiting into that airspace)

Therefore the need to add the 50ft to the forecast terminal QNH MDA/DA (Jepps) if using area qnh

[ovum]

overmars

So am I right to say that en route, I set my altimeter to the Area QNH and before I start my descent, I set the altimeter to the TAF QNH so that I can disregard the 50 ft increase that will be required if I used the Area QNH?

Correct

Q - Oktas8, it worked! Top stuff :ok:

[Defenestrator]

Chuck,

Only three QNH's are given on a 12 hr TAF. One for now, four hrs in, 8 hrs in. The next Qnh will be the first one on the next 12hr TAF. Not that it all really matters.

Cheers:ok:

[ITCZ]

Want some more interview questions?

How is Moderate and Severe turbulence defined?
When are you required to report it?

Which aircraft are required to be fitted with GPWS?

Which aircraft are required to be fitted with TCAS?

Can such an aircraft fly in CTA with TCAS inoperative?

Your IFR CHTR aircraft has an altitude alerting system. It is written up as not providing the aural and visual warnings (approaching/deviating from assigned altitude). Can you take it flying? Any restrictions?

What does a gradient in brackets on a SID chart indicate?

Describe how you make a circling approach to aerodrome YXXX at night.

What are your actions if you lose visual reference whilst circling?

[turbantime]

Only three QNH's are given on a 12 hr TAF. One for now, four hrs in, 8 hrs in.

Incorrect. Chimbu is right in the first place.

Jepp Met 11.16.3 Up to four (4) forecast values of QNH are given, valid at three (3) hourly intervals commencing at the beginning of the validity periods of the forecast.

Where I fly, 99% of the TAF's are valid for 12 hours. We always get four QNH's and Temperatures for the reason above. You will also find that area QNH's on an area forecasts are also only valid for three hours. :ok:

[Defenestrator]

My apologise, I stand corrected. You're absolutely right.

:O :ouch:

[Chimbu chuckles]

turbantime you're right if talking about PEC.

We are required by our SOPs (widebody/longhaul) to add 50' to an MDA to make it a 'claytons' DH if you like...this seems almost universal amonst the big end of town.

It makes sense when you think about it for a second...the DH on an ILS is exactly that...Decision Height and it is perfectly acceptable to go below it slightly during the GA manouver.

An MDA is a Minimum Descent Altitude and must NOT be broken in the GA....so we add 50'. We do not have a PEC in the Boeing.

Another good question...What's the difference between DH and MDA?

Here's another one. Explain the difference between MDA and OCA?

Chuckles.

[overmars]

With regards to ITCZ's questions (another question, how do you define the ITCZ? heh), most of the answers can be found in the AIPs. A bit lazy to get off my bum to find them, but they're there. Except for a few that I am unsure of, for example...

What does a gradient in brackets on a SID chart indicate?

So far, I have only seen 'GRAD 3.3%' on the SID chart that I use. Haven't really seen any in brackets.

And the question regarding MDA and OCA... that's a good one. A colleague of mine said that they are basically the same thing. Somebody please dispute him! That would make my day! :ok:

[turbantime]

Defenestrator,

No worries

Chimbu,

Yeah, I can see the logic behind that.

The gradient in brackets indicates the gradient to be flown to remain in CTA.

I'd have to say MDA is an OCA? Just like DA and minimum obstacle clearance for visual circling are an OCA.

As for DH and MDA. I'd say that DH is much the same as a DA where descent below that height/altitude is allowed as long as the decision to continue/MAP is made at or before reaching that height/altitude? Whereas descent below MDA is not allowed unless meeting the appropriate criteria?

[ITCZ]

Difference between MDA and OCA?

MDA is minimum descent altitude, you can descend to MDA in IMC, but not below.

If you gain visual reference at the MDA, you can descend visually from the MDA to not below the OCA (daytime procedures) and circle. You cannot go below OCA until established on final for the landing runway. The OCA is performance category dependent in PANS-OPS (Cat C = 400') or 400' in australian old criteria charts.

Some more interview/renewal questions from the ITCZ vault.

Questions:
1. What are the Category B speeds?

2. What determines Cat A, B, C, or D?

3. What are the conditions for descent below the minima (circling day, circling night and straight in)?

4. What is the minimum taxi distance behind turboprops and jets (a) taxiing and (b) requiring breakaway thrust?

5. What is the minimum distance from objects when activating the Wx radar on ground with antennae rotating, stationary, and what objects must be outside this distance?

6. What are suitable and adequate aerodromes?

7. What limits apply to the IFR altimeter checks?

8. What are the conditions for visual approach, night and day?

9. What are your actions if landing gear is not locked down after normal selection? (ATC/procedures, not the manufacturer drill to get em down)

10. What are the conditions on conducting straight in approaches to CTAF?

11. Which Australian aerodomes use LAHSO procedures? Can you participate as active or passive?

12. When does a Notam become a 'one-liner'?

13. What does Nil Current with respect to a Notam mean?

14. What fuel reserves apply to normal, one inop and depressurised ops/PNR?

15. What are the speed limitations in the holding pattern?

16. When are your required to plan for an alternate aerodrome?

17. When can you use Special Alternate Minima?

18. You are planning to depart ASP RW12 to the north in IMC. How do you ensure terrain clearance until established above LSALT on track?

19. You are an IFR flight planning AS for TNK, you are having trouble getting an AVFAX briefing. What are the minimum briefing materials you require prior to departure?

20. When is a FROM period valid in an aerodrome forecast? Is different if the FROM is in a TTF?

21. How many flight attendants do you require in the cabin whilst refuelling?

22. What is the wake turbulence separation standard for a Medium category aircraft departing behind: a B747, a Metro, a Chinook?