Tech Q's....

[Alcatraz]

#3: What would you clasify as the biggest hazard in heavy rain on final approach?

Either that there's grapefruit size hail in it, or that I'll lose both engines. But, yeah, the windshear thing sucks, too!

 

[FatesPawn]

Exceedance of hold over time does not nec. constitute accumulation. I think what the question is stabbing for is the fact that we should clean off the old type 4 with type 1 before re-applying new type 4.

Why would you get "re-deiced" just because your holdover time expired without additional snow/ice accumulation? -FZRA? I guess that's the only time, huh?

If it's an interview answer, just say type 1 then type 4 to get re-deiced. When they question you further, your dazzle them with your Flightinfo level of understanding of their new question.

 

[FatesPawn]

In a constant speed, unaccelerated climb or descent, lift only has to counteract the component of weight perpendicular to the flight path plus the aerodynamic tail-down force. Even in unaccelerated straight and level flight, lift is GREATER than weight because it still has to support the tail-down force plus the weight of the aircraft.

I'll agree with everything you stated...

However... the original question was "in what phase of flight was lift the greatest..."

So, my answer still stands. Steep turns (jokingly meaning any accelerated flight) In all other "unaccelerated" phases of flight lift is going to be constant. Unless of course, your 350lb Flight Attendant comes up front to bring you your crew meals (thereby shifting the CG Forward affecting your down force on the elevator requiring more total LIFT to be generated.)



So, the correct interview answer to "During what phase of flight is lift the greatest" is:

The phase where the stew brings me my cocktail.

-fate

 

[avbug]

Steep turns.... otherwise a 1,000,000 lb. aircraft always generates 1,000,000 of lift regardless if it's landing, taking off, or cruising.... The only time an aircraft generates more lift than it weighs is during "accelerated" flight. Private Pilot 101.

Someone's teaching the private pilot bad information. Lift is greater than weight in a banked level turn. Lift is less than weight in a climb or descent. Lift is greater than weight in a level turn. An unloaded, descending turn, this isn't the case, and the values vary in a climbing turn, too.

Icing protection varies with what's available, and the nature of the icing. Type 1 fluid may or may not need application again. Holdover times are not science; a published time may still be good, but the ice may be building and the properties failing due to ambient conditions; that's the reason for the contamination check. Likewise, a published holdover time may have expired, but there may be no additional ice forming...again, the reason for a contamination check.

De-ice and subsequent anti-icing applications aren't there to keep controls from "gumming up." The purpose of removing ice is aerodynamic; it's making clean wings and a clean airplane, which includes removing ice which could cause engine damage or flameout, ice which might cause structural damage, and ice which destroys lift and alters aircraft performance and flight characteristics. In other words, all the frost and all the ice (save for that under the wing in the vicinity of the fuel tanks).

When performing two-step de-icing/anti-icing, the freezing point of the fluid used for the first step cannot be more than 3 °C ( 5 °F) above ambient temperature. The freezing point of the type I fluid mixture used for either one-step de-icing/anti-icing or as a second step in the two-step operation must be at least 10°C (18°F) below the outside air temperature. In no case may this temperature be lower than the lowest operational use temperature (LOUT).

Type II, III, and IV fluids used as de-icing/anti-icing agents may have a lower temperature application limit of -25°C (-13°F). The application limit may be lower, provided a 7°C (12.6°F) buffer is maintained between the freezing point of the neat fluid and outside air temperature. Again, in no case may this temperature be lower than the lowest operational use temperature (LOUT). Under no circumstances shall an aircraft that has been anti-iced receive a further coating of antiicing fluid directly on top of the contaminated film. If an additional treatment is required before flight, a complete de-icing/anti-icing shall be performed Puting anti-ice on top of existing ice means you're protecting the existing ice, not a clean surface...comes back to knowing the condition of the aircraft, and that depends on a number of factors. Ensure that any residues from previous treatment are flushed off. Failed de-ice fluid usually changes from glossy to opaque, but in presence of freezing rains that produce glossy surfaces, de-ice failure may be difficult to detect visually.​

​

If applied fluid is unable to melt or absorb contaminants, it must be applied again; aircraft must be de-iced again. Ability of fluid to do it’s job is a result of it’s mixing ratio, which becomes diluted by the contaminants on the aircraft. As the fluid becomes colder, it becomes more viscous. At some point, it becomes too viscous (sticky or thick) to shear off the aircraft, and becomes an aerodynamic hazard--the anti-ice fluid has become the hazard). LOUT, or Lowest Operational Use Temperature, is the lowest temperature at which a fluid may be used. It’s the warmest of either the aerodynamic acceptance test (shear value) of the fluid, or the freeing point buffer value. If the freezing point of the fluid is within the freezing point buffer of the fluid (100C above freezing point for type 1 fluid, or 70C for type II, III, or IV fluids), the fluid cannot be used. In other words, if the freezing point is –350C, add 100C to get –250C…OAT must be greater than 250C.​

Don't get too wrapped up in holdover tables and tiems. Holdover time begins when the final application of deicing/anti-icing fluid commences and expires when the deicing/anti-icing fluid applied to the aircraft loses its effectiveness. Again, you may be well within your holdover times, and the fluid may have lost it's effectiveness anyway. As the pirates might say, aaarg matey, thems times is more like guidelines, than rules...

Heavy rain on final...you have descending liquid precip, which means you've also got descending air. You have several things to think about. In no particular order...microbust potential, and your microburst/windshear escape maneuver (brief it), your missed approach procedure, windshear and turbulence (a possibility; may or may not be relevant, depending on the type of rain and the cloud and conditions that are producing it), reduced visibility, the possibility of a lightening strike, and the wisdom of holding until the storm passes, or diverting as necessary. You should also consider the possibility of freezing rain, as conditions warrant, and hail, too.​

What kind of comments would you like on venturi throat velocity changes? Restrict airflow through a venturi, see a velocity increase, pressure decrease, and temperature drop.​

MLS/GPS...allows infinite possibilities in flight path guidance; curved, around obstacles and terrain, all sorts of things that a linear fixed localizer or VOR cannot do, and it can accomplish this in the horizontal and the vertical, providing customized precision guidance to a runway that would otherwise not be able to sustain an approach due to terrain or obstacles. It can produce lower minimums than would be allowed by conventional approachs such as an NDB, VOR, LOC, or ILS, particularly in consideration of terrain and obstacles.​

For ETOPS, the following ratings are awarded under current regulations according the capability of the company or airline:

• ETOPS-75
• ETOPS-90
• ETOPS-120/138
• ETOPS-180/207

However, ratings for ETOPS type approval are fewer. They are:

• ETOPS-90, which keeps pre-ETOPS Airbus A300B4 legally operating under current rules
• ETOPS-120/138
• ETOPS-180/207, which covers 95% of the earth's surface.

Which is higher on the B747-400...Vmca or Vmcg? Vmcg is higher, but remember that the numbers vary with aircraft loading, and ambient conditions. There are no specific numbers...the numbers where control is ineffective or lost depend on a number of factors ranging from CG location to crosswind, etc.


Vmca and Vmcg refer to controllability, but are related to slightly different factors. For example, Vmca may be affected by bank angle, whereas Vmcg cannot (for obvious reasons). Conversely, Vmcg is dependent upon the coeffiient of friction between the aircraft landing gear and wheels, and depends on surfac winds and conditions, whereas Vmca does not. Most significant for you here is the distance between the control surface counteracting Vmc (a) or (g)...and the fulcrum. In the case of Vmca, the fulcrum is the center of gravity, and in the case of Vmcg, it's the pivot point for the gear. The relationship between the two depends on aircraft loading, and the specific aircraft in question. In the case of the 747, the arm between the rudder and CG is greater than the arm between the rudder and the pivot point of the gear, which means that the arm is shorter for ground control, less rudder effect is available until a higher speed, and Vmcg occurs at a higher number.

 

[ASH]

Hot dog avbug. Much appreciate the great reponse.

So, how could we reduce Vmcg?

 

[avbug]

Reduced power takeoff.

 

[FatesPawn]

Someone's teaching the private pilot bad information. Lift is greater than weight in a banked level turn. Lift is less than weight in a climb or descent. Lift is greater than weight in a level turn. An unloaded, descending turn, this isn't the case, and the values vary in a climbing turn, too.

No, I think Private pilots are being taught exactly what they need to know. Notice I didn't say ATP 303

Had I knew these were silly interview type questions, I would have put on my cypherin cap and posted some intricate scatter graphs to dazzle the crown imp:

... but I have to ask - and fear the retribution of flightinfo gods for my lack understanding - but how in the world is total lift less than weight during a straight descent? I just can't believe it....

-fate

 

[BEECH-SLAPPED]

... but I have to ask - and fear the retribution of flightinfo gods for my lack understanding - but how in the world is total lift less than weight during a straight descent? I just can't believe it....

If you reread my first post, it explains that in an unaccelerated climb or descent, lift only has to oppose the component of weight PERPENDICULAR to the flight path plus the tail-down force. That perpendicular component mathematically is:

WEIGHT * COS(ANGLE of CLIMB)

For example, a 100,000 aircraft with a 10 degree climb angle has a perpendicular weight component of 100,000 * COS(10) = 98481 lbs.

However, depending upon the CG location, the tail down force required may significantly add to the required lift. As a simple example, let assume that the CG for our ficticious aircraft is 5 feet forward of the center of lift. Also, lets assume that the center of aerodynamic force on the tail is 75 feet AFT of the center of lift. Balancing out the moments, this yields a tail-down force of 6565 lbs. So, the total lift required in this climb would be 98481 + 6565 = 105,046 lbs. That's over 5000 lbs more than the total weight of the aircraft!
So, in this case the lift required is GREATER than the weight of the aircraft.

Wil this always be the case? No, because these values drop off dramatically with an increased climb or descent angle. What is the perpendicular component of weight in a 90 degree climb? Zero! However, there are still aerodynamic moments produced by the wing that will have to be countered by the tail, so even in a straight up climb, there is some lift being produced.

So, I think that the main point here is not what the actual value of lift is compared to the weight, but how this value changes in climbs and descents for the same conditions. Our 100,000 lb aircraft will require MORE lift in straight and level flight at 200kts than the same 100,000 lb plane climbing at 200kts. Why? It's all in how the perpendicular weight component changes with angle of climb.

 

[avbug]

No need for ATP 303 to teach correct information.

Next thing you'll be telling us that ground effect is a cushion of air beneath the wing...

 

[FatesPawn]

Beech,

Thanks for clearing my question to avbug. I sincerely appreciate it. Good explanation.

-fate

... but I have to ask - and fear the retribution of flightinfo gods for my lack understanding -

No need for ATP 303 to teach correct information.

Next thing you'll be telling us that ground effect is a cushion of air beneath the wing...

Thanks. I thought it would take 2 or 3 posts for the retribution. Wrong again.