density altitude

[BrendAn]

interesting video from hoover about an accident in high terrain.

 

[turboplanner]

Experienced pilot; this was a tricky one because of the focus on photography.

Density Height will be important in some of the areas you intend flying, because if you just get in and go like a local flight, the ending can be very different.

If your instructor teaches PPL you'll learn all about it in Performance & Operations before the NAVEX phase of training. ( haven't heard anyone on here say that RA teaches it.)

 

That includes calculations for: 

• Pressure Height
• Density Height
• ISA (International Standard Atmosphere)
• Pressure decrease with Altitude increments
• Temperature decrease with Altitude increments
• Take Off and Landing Charts
• QNH > ELEV PH > OAT > DH > Takeoff Distance > Landing Distance > Takeoff Speed > Landing Speed > AUW > Wind Component. 

Armed with that you'll handle flights from airfields with different altitudes and flights from cold coastal airfields to hot inand airfields, and vice versa.

 

[Reynard]

Of course, now there is a handy App for that.

AutoDens…….and if you’re feeling particularly lazy or mathematically challenged, there is also an app for TODR that can be configured for your specific aircraft.

 

As long as you are across the principles involved.

[turboplanner]

33 minutes ago, Reynard said:

As long as you are across the principles involved.

That's why we have training; to learn those principles.

Yes, the calcs are easy, yes you could get an app or make an app, but

(a) if you don't understand the principles and input the correct figures or

(b) You don't recognise when you need to, you're going down.

 

That's why this Flight Instructor> United Airlines pilot > 5,750 hours > 130 hours on type slipped up.

 

Another classic example is this one: 

The runway looks dead flat, probably just like his home strip.

Why would you do the calcs here?

Would you have check the strip for height at the takeoff end, then the end of strip, start of treeline against the aircraft capability?

Maybe spent some time in a climbing circle directly above the strip to provide a forced landing point?

The pilot here didn't just have 1, 2, 3 No Go points - he had about seven - the longest failure to act that I've seen.

You won't get that on an App.

 

 

 

 

 

 

[RFguy]

the history books are replete with people loading up their airplane at high aerodromes with high DA and crashing into the opposite mountain....

It's easy enough to make a laminated table on the back of your checklist.

 

I can and do-do DA in my head before takeoff (ability to depart on intended path)  and landing (in order to consider the go around scenarios) .

On the back of my checklist is a table of weights, DAs driving  that points to climb rates, runway rolls, stall speeds, TOSS and bank speeds.

I have a postit note I stick on my instrument panel that I write the above for planned TO and landing.

 

[Reynard]

Back in the day I had a laminated set of nested curves for TODR as a ready reckoner.

These days, I can see the advantage of a purpose-built app as it actually may encourage people to check the TODR because it makes it so simple.

 

[spacesailor]

It's a wonder that we have flyable aircraft.

If Orville Wright didn't know all the tables our new pilots have to learn before 

getting into that left seat .

spacesailor

[facthunter]

The RIGHT seat is the Left  seat as you can make all your OWN mistakes there. Some won't GET that.

    It's a delicate balance. You have some luck and some skill.. The trick is to get enough skill Before you use up all your luck.. Learn from the mistakes of others. You don't live long enough to make them all yourself..  WHEN you think you know it ALL THEN you are getting really dangerous  Nev

[RFguy]

You are right about  luck/skill... The other day I encountered prop wake turb landing right behind a cessna 206 that had done a short fielder (dragging it in at probbaly high thrust) and then  go around (all thrust) .

There was nil wind, and when, in the flare with power off,  I got tossed around--- right at the time I was the most vulnerable (low control authority, low speed) . 

I was like 'WTF ?!  I was tossed around  in roll and yaw. was quite a surprise.

I applied a little bit of power to stabilize, and almost not quite enough as I got lifted up 10 feet in some wierd turb gust and then almost ran out of airspeed . I should have applied full power and turned it into a go around, or at least got airspeed all the way back up and had another go at the landing (there is 1600m of runway ) . I used up a bit of luck..... I've only encountered such turb once before a couple of years ago with some mech turb from a line of hangers downwind somewhere else next to the runway .....

 

Which brings me to this- that it's important to fly regularly- because the more often you fly , the more often you encounter adverse conditions, and the more likely you will have recency -  to competently handle whatever has been thrown at you.

That is to say, if you fly not often enough, you might encounter that prop wake turb once every year, which is not often enough that your brain has recency  to deal with it competently / instinctively. Fly once or twice a week,  and you are more likely to encounter that type of adverse condition  often enough that  it has not been too long since you last dealt with something like that... if that makes sense.

[facthunter]

One of the advantages of NOT flying for a living is you can CHOOSE when and where you fly. Who in their right mind would want to fly at 3 am in the morning and do a challenging Instrument approach at the end of it?  Nev

[turboplanner]

1 hour ago, spacesailor said:

It's a wonder that we have flyable aircraft.

If Orville Wright didn't know all the tables our new pilots have to learn before 

getting into that left seat .

spacesailor

In the AUF days RA got their exemptions from CASA on the basis of flying in paddocks, below 300 feet and from memory at least 5 Nm from the nearest airfield, so you wouldn't have needed tables and calculations.

Then manufacturers got involved and built bigger and faster aircraft and even though RA was founded on affordable budgets they wanted to include cross country flying, at least with relatively short distances. Orville didn't do that so it didn't matter.

If you're flying from Airfield A at seal level to Airfield B in the mountains you have to know how to calculate the different heights and runway requirements and whether you can get out again. Same applies if you are travelling from a cold airport to a hot one or starting on a cold morning with frost and ice on the ground and landing 4 hours later in 40 degrees. The environment we fly through is far from static.

[spacesailor]

Even to fly circuits , from your home field. 

Or , a road trip to another airfield. 

You are trained to a higher classification than you need , for the old AUF. 

spacesailor

 

[turboplanner]

1 minute ago, spacesailor said:

Even to fly circuits , from your home field. 

Or , a road trip to another airfield. 

You are trained to a higher classification than you need , for the old AUF. 

spacesailor

 

Don't get carried away, for circuits from your home field you're not going to be landing a couple of thosand feet higher are you?

but if you do tow the aircraft to a higher altitude airfield it will perform differently so you have to sum up whether you can take orr and climb out. 

[skippydiesel]

The big lesson I took from this video is pilot fixation -  I could just imagine him willing that aircraft to fly, ignoring how long it took to get into ground effect/followed by a touch down and then a limited climb all the while running out of a very long runway. 

 

Pilot fixator is a real phenomena - (been there). To my thinking its way more dangerous than all the other factors that the pilot should be taking into account and doesn't.

[BrendAn]

It's amazing to me that the telluride

Airstrip in the video is 2000 feet higher than mt Kosciusko.

[RFguy]

35 deg C at Goulburn.... 998 hpa ...  not unusual for summer.

altitude 2139 ft.

std temp = 15-4 = 11C

35 deg above 11 = +24 above std temp x118.8 = 2851

1013-998 = 25hpa x 30  =750'

total DA = 2139+750+2851 = 5740'  . quite alot eh 

my 50' altitude T.O. distance increases from  579m at  11degC & std pressure   to  854m.  (at gross). quite a bit. about 50% increase.

[facthunter]

Your rate of climb is devastated also and you are closer to your service ceiling.   Nev

[RFguy]

ROC (gross)  falls from 630fpm to 450 fpm. 

[facthunter]

 A Service ceiling is when the climb rate MAX's at 500 FPM.    500 fpm is also known as "standard rate.". Nev

[aro]

8 hours ago, facthunter said:

A Service ceiling is when the climb rate MAX's at 500 FPM.

I think that number is for jets. For other aircraft the number is usually 100 fpm I believe.

[facthunter]

News to me if it is. Think, Usually and Believe?  I'm sure I first referenced it long before I thought I'd be flying jets Standard rate applies to both  climbing AND descending  IF you want relief from the requirement  when climbing you can ask for a cruise climb  It's used to aid in separation. If you are cleared for descent unless "WHEN READY" included you must commence it within a minute and have exceeded and  will as a minimum, maintain. standard rate'. Service ceiling and absolute ceiling are usually specified in an aircrafts performance details. The reason I mentioned it was relating to the Density altitude issue. Equipped with the knowledge of what it nis AND being aware of your current DA you have an idea of what extra performance  to climb you have left. At the absolute ceiling you have NOTHING Left, Raising the nose doesn't do anything for the climb You are just dancing at the stall Point..  Nev

[aro]

9 hours ago, facthunter said:

Think, Usually and Believe? 

That just means I found enough references to convince me, but not something to quote as a primary source.

But the FAA has it: https://www.faa.gov/sites/faa.gov/files/13_phak_ch11.pdf (p 11-8):

The service ceiling is the altitude at which the aircraft is unable to climb at a rate greater than 100 feet per minute (fpm).

 

If you're familiar with Cessna 172 performance, 500fpm is obviously wrong. That would give a service ceiling somewhere around 5000'. The actual service ceiling is given as 13500.

[djpacro]

1 hour ago, aro said:

…. The service ceiling is the altitude at which the aircraft is unable to climb at a rate greater than 100 feet per minute (fpm). …… If you're familiar with Cessna 172 performance ….

Yes indeed. I lived in Wyoming USA for several years and flew a 172 (along with other types) from an airfield at 6500 ft elevation with summer temperatures up to 30 deg C. Illuminating.

 

 

[pmccarthy]

The service ceiling of your Sopwith Camel is when you raise the nose to fire at a Hun fifty feet higher, and you fall out in a spin.

[facthunter]

A few times  flew  a medical request" whooping cough" trip in a 172 to around fl 140  That's was it 3 up and no fatties in those days. If you don't HAVE  and use mixture leaning you won't get that far. Temp must have a big effect. Geoffrey Dehavilland got a DH 60 to 23,000 feet in 1923 OTA. That's recorded and a good effort The highest I managed to get a DH82 to without mixture leaning was FL135 in  the middle of Winter and I used under cloud  (up draft) assistance at few levels. Also I had a NEW C172 at Gyra on a hot day and it would barely fly. Pick a point  where is it's not flying convincingly at you abandon the take off. Pace it out personally. Mt  Hotham I treat the same. using the POH figures in a Mooney 2 up. Do a spiralling  climb to help you get to a good landing spot en route if the donk quits. Watch Albury CTA limits and powered chute activity  east of  Bright. Pick good weather cloud wise and best verified by some one on the ground  en route who has flying savvy.. Nev