More Tricky Interview Questions

[Tetauy]

MSA?

I agree with KingAirer.

#7 - MSA - remember it is only supposed to be used in emergency situations. If you are in an emergency situation and can not maintain altitude because of single engine, for example, then the MSA assures you 1000 ft obstacle clearance with the 25 NM of the Navaid it is centered on unless otherwise charted.

Way to go on the rest of them. I learn something new everyday.

 

[FurloughedAgain]

Looking for answers.

Has anyone been able to find a firm answer to #5 or #12?

Thanks!

 

[Swaayze]

Factors affecting V1: acft weight and configuration; runway length, slope, contamination; density altitude


V1 is affected by a contaminated runway.


As for the TAS - Mach questions, who knows. I have never paid much attention to my TAS vs. SAT readings on the MFD (now I have something new to occupy my time, thanks). You don't have complete info, but my first guess is that your TAS (Equivalent corrected for Temp, yes?) is going to be higher at the higher FL, even though your indicated would be much less. BWTFDIK.

*(edited)*Falcon is correct in that the speed of sound varies proportionately to Temp, so I suppose TAS would be greater at 290 if air density weren't a factor in TAS. Are we talking indicated Mach or True Mach? And would the density change make enough difference to change the answer? HellifIknow. "**CENSORED****CENSORED****CENSORED****CENSORED**it I have lots of time and experience and I can make the autopilot fly a great ILS. Just hire me, you won't be sorry. I promise. Please!!"

Jeeez I need a beer.


BTW, there is no chime associated with the ICE DETECTED cas message, on the jet anyway. But I like the way you think. (bonus points for me)

 

[Singlecoil]

MSA

One more note on MSA. It only guarantees you 1000 feet of clearance at standard temperature. Remember, if it is colder than standard, your altimeter is lying to you.

On a cold day in Alaska or Montana, i.e. minus 30, you can be several hundred feet lower than your altimeter is indicating. This is not a problem unless you are in mountainous terrain. It all depends on how much higher the obstacle is than the elevation the altimeter reporting station is at.

If the MSA is for a 4000ft AGL mountain, the error in the above conditions can be as much as 700 feet if memory serves, yielding a 300 foot clearance at MSA.

Ever notice that even under radar vectors you get more ground prox warnings in the winter? Same reason. Minimum vectoring altitudes can be as low as 1000 feet AGL even in MOUNTAINOUS TERRAIN. I've queried controllers on this, and found they have very little knowledge of altimetry, or the fact that the airplane is actually lower than indicated on the instrument, and via mode C , lower than indicated on the radar screen.

 

[FurloughedAgain]

V1

"V1 is affected by a contaminated runway."

Could you explain this and/or provide a reference please?

Thanks in advance!

PS - You're right about the CAS message. No chime! I'm writing honeywell! I cant see blue cas messages through the newspaper!

 

[Tetauy]

Nice one Singlecoil. I just thought about the definition and not what actually happens during different weather. Thanks for getting my thoughts flowing in that direction.

 

[Swaayze]

A contaminated runway *may* affect V1 due to the increased stopping distance required during an abort. In this case you would have to make your no-go decision earlier if on a short runway.

 

[80/20]

#5. What are some factors which affect V1?

Think of V1 as a range of speeds rather than one fixed speed.
The V1 range is restricted by Vmcg (low V1) and accelerate stop distance (high V1). Many good definitions are already given in the previous postings - ref. FAR 25.107.

A typical interview follow up question would be about practical usage. How do you use that information in real life?

Some considerations are:
1) To avoid weight reduction
2) Improve safety if the runway is contaminated
3) Use reduced thrust if possible

A high V1 will increase the safety margin for continued takeoff.
A low V1 will increase the safety margin for a rejected takeoff.

A contaminated runway will influence the stopping distance.
Poor braking action = longer stopping distance
Slush = slower acceleration
A slippery runway may also affect Vmcg - some flight manuals contain different Vmcg values for wet and dry conditions ref. FAA Order 8400.10

Some manufacturers recommend reducing V1 if the braking action is poor.

Another advantage of a low V1 could be to avoid a weight reduction for brake limited takeoffs, usually at high altitude airports.

Be alert and watch out! Interview failure cause number one is not to notice the QBQ. (Question Behind the Question).
Are they in reality concerned if you can not quote each theoretical fine point? Or are they on the lookout for something totally different such as your attitude and people skills?

 

[freightdogfred]

The primary factor affecting V1 speeds is aircraft weight. There are other variables that will affect it such as flap settings. The runway contamination factor mainly deals with VMCG issues, evidenced by De-rate power charts not being runway specific-it's a function of temp and weight, and to some extent wet/dry. Douglas had nifty cold/wet/ice charts for the DC-8 and Boeing likes to tinker with V1 with their "Improved climb" chart (Increase V1 and VR for a higher climb speed, improving second segment climb thus a higher weight) In a basic nutshell, higher weight and slippery runway=Higher V1

 

[80/20]

Good point freightdogfred - basics first - the foundation for V1 is aircraft weight.
AFMs will give a V1 for balanced field takeoff (for each flap setting and condition).
Using a higher or lower V1 can result in an unbalanced takeoff.
Higher V1 may be used for improved climb, but can not exceed VR or VMBE.
Lower V1 may be used to improve stopping margins on slippery runways.

One of my former DC-8 operators had only approval for balanced field takeoffs while my current Boeing job involves a lot of winter operations where V1 reductions are approved and often used.

Guppy? Sounds like a good old Buffalo guy?