How about the more modern day crashes ?

[Zipper730]

They the investigators "THINK THEY MISS READ" the altimeter

There was no CVR on the aircraft so they didn't know for sure. The altimeter design was prone to be misread and a study was done to this effect. The aircraft's position was known via the SAGE system.

It is just another excuse for either not knowing the real reason or just an answer to cover up the real reason. I wonder how many of those reports are still classified secret?

I didn't know NTSB reports were top secret

 

[FLYBOYJ]

They the investigators "THINK THEY MISS READ" the altimeter, that sounds like people that should not have a pilot certificate. It is just another excuse for either not knowing the real reason or just an answer to cover up the real reason. I wonder how many of those reports are still classified secret?

OK - a few things - an instrument rating is very hard to get. By the time you're flying higher performing aircraft most (and I emphasize most) pilots are highly proficient, especially if they're flying with the airlines or corporate aircraft. When civilian aircraft crash there are no "classified" reports, the NTSB gets involved and will research the accident until they come up with a probable cause. Every so often you will have a commercial airliner go in due to some malfunction or complacency on the part of the crew. In the US those incidents are extremely rare with the major airlines (look up the NTSB accident statistics). Read the official NTSB reports and filter the operation of aircraft, I bet most of the accidents you're looking into involved GA aircraft

 

[FLYBOYJ]

I didn't know NTSB reports were top secret

They'll keep portions of the investigation under raps, may come out with a press release as the investigation is ongoing but will release all their findings at the end of the day

 

[DerAdlerIstGelandet]

They'll keep portions of the investigation under raps, may come out with a press release as the investigation is ongoing but will release all their findings at the end of the day

For the most part what I have seen they are eventually released to the public. You can go to the NTSB website, and download the final reports. I have been perusing them quite a bit lately for a work project I am working on.

 

[mikewint]

Altitude is not as simple a concept as it might seem when dealing with aircraft. In the context of flight one must be very careful to know the "type" of altitude being discussed. INDICATED altitude is what the aneroid altimeter reads. ABSOLUTE altitude is the reading on a radar altimeter. TRUE altitude is the distance above Mean Sea Level corrected for non=STP conditions. There are others such as DENSITY altitude very important to Helos and heavily laden aircraft. PRESSURE altitude is the elevation above a standard usually one standard atmosphere (1013.25 millibars) use to indicate "Flight Level" in the US Class A air space above 18,000ft.
So depending upon the type, a basic altimeter is just a device that measures air pressure which varies with altitude. There are radar altimeters which send radio pulse toward the ground and measure the return time. They will accurately indicate the distance to the earth surface but they are expensive, heavy, and complicated.
The "trick" with the first type is in remembering to set the altimeter to the correct airport altitude and weather conditions. For example if your aircraft were sitting on the ground at an airport that was at MSL, 59F, and 29.92inHg barometer. Your altimeter correctly reads ZERO. Now you leave and return the next day. Conditions have changed, a Low has moved in and the airport barometer indicates a reading of 29.42inHg. The altimeter of your aircraft will now indicate that you are at 500 feet! Remember it (altimeter) is just a sensitive barometer. So imagine a pilot forgetting to set his altimeter at that airport on that day flying in a heavy overcast/fog. His altimeter will be telling him that he is 500 feet ABOVE the ground when he smashes into it.
In flight you face the same sorts of problems. Let's suppose you are flying at 5,000 feet. Your flight path takes you into a Low pressure front. As the outside pressure drops within the low your altimeter will RISE, you lower the nose to return to a reading of 5,000 feet. Depending on the nature of the Low you might drop down to an actual 4,000 feet while your altimeter indicates 5,000 feet. Too bad about that 4,100 foot mountain in your flight path.

 

[DerAdlerIstGelandet]

Mike, Density Altitude is very important to all types of aircraft regardless of being heavy, or fixed or rotary wing. Air density is probably the most important factor affecting an aircrafts performance. It effects everything from lift, prop/rotor efficiency, and the power output of the engine.

Try taking off from a high altitude airport on a really really hot day.

 

[GrauGeist]

It was interesting to see the fluctuating Density Altitude reports coming out of Benton Field (O85) during our heatwave just shortly before the Carr Fire broke out!

 

[mikewint]

Chris, Thanks, I do realize how much "thin" air affects all aspects of aircraft performance. I have friends who are pilots and have flown with them several times. Hot and humid air is also low density as more and more light H2O (18) molecules replace heavier O2 (32) and N2 (28) molecules. My thought was that while it (low density) affects all aircraft, the effect is more severe on helos and heavy aircraft.
In the US Leadville, CO located above 10,000 feet can have a summer altitude density of over 13,000 feet. Take-offs a bit hairy?
In Nepal Fishtail Air will fly helos to Camp 2 at 21,000 feet (6400 m). Their helos are rated to 23,510 feet (7026 m) and have flown as high as 7400 m

 

[DerAdlerIstGelandet]

It effects everything...

 

[PWR4360-59B]

It was interesting to see the fluctuating Density Altitude reports coming out of Benton Field (O85) during our heatwave just shortly before the Carr Fire broke out!

That is interesting, how far was the fluctuation and what was the dominate ending pressure, high or low?

 

[GrauGeist]

Benton's elevation is 723 feet and at one point the reported density altitude was over 4,000 feet (going by memory, but I believe it was 4,120). Exeptionally low dew point, air temps in the neighborhood of 110 degrees plus, not sure how high the pressure got, but it was substantial.

This is also one of the reasons the Carr fire literally exploded into a firestorm

 

[mikewint]

My home airport Baxter County is at 929 feet MSL. Today at this time the temp is 80F, dew point is 74F and the airport barometer reads 29.95inHg. The calculated density altitude is 1697.3 feet

 

[PWR4360-59B]

Benton's elevation is 723 feet and at one point the reported density altitude was over 4,000 feet (going by memory, but I believe it was 4,120). Exeptionally low dew point, air temps in the neighborhood of 110 degrees plus, not sure how high the pressure got, but it was substantial.

This is also one of the reasons the Carr fire literally exploded into a firestorm

That 4000 plus is low pressure barometric. So you said pressure also got exceptionally high as well?????? Or just the density altitude?
It would be nice to know the for sure barometric pressure there.

 

[GrauGeist]

That 4000 plus is low pressure barometric. So you said pressure also got exceptionally high as well?????? Or just the density altitude?
It would be nice to know the for sure barometric pressure there.

Not sure about the specific barometric pressure, but it was noted to have been quite active as the heat wave was building up - we had a week straight with triple digits, exceptionally low dew point and humidity in the mid-teens.
I'll be stopping by Hillside Aviation tomorrow, I'll see if they have a copy of that and if so, I'll share it here.

 

[gumbyk]

Fluctuating Density Altitude is normal. e.g. a 16ºC fluctuation of temperature between daytime and nightime will give an 8,000ft density altitude correction difference. It's if there are rapid fluctuations in temperature that its a real problem; so if the wind changed and was blowing off the fires, then I'd expect it to have increased suddenly.

I was always taught not to do performance calculations more than an hour before take-off, and be aware of the temperature when you did it. Pressure isn't so much of a concern as it doesn't have as big an effect of Density Altitude as temperature does.

 

[GrauGeist]

The Redding area is at the north end of the great central Valley, ringed on three sides by mountain ranges: The Coastal and Klamath to the west and north-west, the Cascades to the north and north-east and the Sierra Nevada to the east.
All the heat in the north end of the valley builds up and creates a high-pressure system that typically prevents marine moisture from getting into the area and the daytime temps can rival the high-desert on the southern end of the state. As the day warms, it quickly draws the cooler air up out of the Sacramento Delta, which interact with the cooler air coming out of the canyons and mountain passes.

It can make for interesting flying conditions.

 

[gumbyk]

The Redding area is at the north end of the great central Valley, ringed on three sides by mountain ranges: The Coastal and Klamath to the west and north-west, the Cascades to the north and north-east and the Sierra Nevada to the east.
All the heat in the north end of the valley builds up and creates a high-pressure system that typically prevents marine moisture from getting into the area and the daytime temps can rival the high-desert on the southern end of the state. As the day warms, it quickly draws the cooler air up out of the Sacramento Delta, which interact with the cooler air coming out of the canyons and mountain passes.

It can make for interesting flying conditions.

Current pressure in Redding is about 995hPa, which is 18hPa below standard = 540ft elevation.

 

[GrauGeist]

Current pressure in Redding is about 995hPa, which is 18hPa below standard = 540ft elevation.

Redding Muni (KRDD) is about 504 msl and Benton Field (O85) is 723 msl - I'm looking at Redding's METAR data and it looks like the Density Altitude peaked by 14:22 this afternoon at 3,435 ft., data at the time: 98F, 24% humidity, and pressure being 29.79in. - also interesting to note that the winds were between calm and 12 knots all day.

RDD's geographic location is down in the valley, east of town, O85's location is up on a plateau overlooking the west side of town.

 

[mikewint]

Redding Muni (KRDD) is about 504 msl and Benton Field (O85) is 723 msl

Holy Cow Dave, I'm here in Arkansas and you be in Colo and I'm 400 feet MSL HIGHER than you???

 

[GrauGeist]

lol Mike - I'm in California!

And Redding is nestled in the north end of the great central valley, with the mountains directly all around us. Matter of fact, Weaverville, the town where my Mom lives is less than 20 miles (as the crow flies) to my west and their airport (O54) is 2,350 MSL.
Trinity Center airport (O86) is situated on Trinity Lake and is a little north-west of Redding by about 15 miles, they are 2,399 MSL.
Dunsmuir airport (1O6) is about 30 miles north of Redding and sits at 3,258 MSL.
Weed airport (O46), which is roughly 40 miles north of me, is 2,938 MSL.
Shingletown airport (0Q6), which closed recently, is east of Redding and is 3,880 MSL.
Burney/Fall River Mills airport (O89) in eastern Shasta County (east-northeast of Redding) is 3,323 MSL.
And Red Bluff airport (RBL) is about 20 miles south of Redding and is 343 MSL.

So this gives a fairly good idea of the local topography just by seeing the elevations of area fields.