Forum: General

Even if it swithes to BARO, you're telling me that it's still dependent on whatever setting is in the Kolsman window? I didn't think an F-16 would be dependent on this as a C172 would.

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Yup, we set out QNH like everyone else. It's fun to taxi behind another viper and see your HUD scales dance around.

<b>QNH</b> is a Q code used by pilots, air traffic control (ATC) and low frequency weather beacons to refer to the current mean air pressure over a given region at sea level (if there is no sea, this is a virtual value by adjusting the value at the ground for its elevation), the "regional pressure setting".

This value is used by pilots to calibrate the altimeter on board the aircraft, to ensure that the pilot is accurately aware of his actual flying height. The QNH allows a pilot to know his altitude with respect to mean sea level ATC may update pilots with the QNH on a regular basis.

In most parts of the world, QNH is given in millibars (or, expressed more correctly, hectopascals, which is the SI unit). In the United States, QNH is given in inches of mercury.

<b>QFE</b> refers to the current air pressure which will calibrate the pilot's altimeter to give actual height above the ground at a particular airfield. This setting is used during take off and landing and when flying in the circuit. A mnemonic for the code is "Q Field Elevation". ATC will update pilots with the QFE when necessary.

In short:

QNH = air pressure referred to mean sea level, given in hPa and mmHg
QFE = air pressure referred to runway-end altitude, given in hPa and mmHg

See also: http://www.f-16.net/modules.php?op=modl ... p;letter=Q

I knew all that stuff Lieven, thanks... I just wanted to know what QNH stood for, I know what setting an altimeter means, I'm almost instrument rated Wink

Reason I ask is I have NEVER heard it refered to as QNH. Then again, I don't fly at military airfields, and when getting ATIS or a departure clearance, it's always refered to as 'altimeter' or 'altimeter setting', and it's in inches of mercury. This is then set in the Kolsman window of my altimeter. This is very critical, especially when flying IFR, because you could really end your day in a bad way if your flying to minimums and you're not at the DH you should be at. What got me was that I was surprised an INS equipped aircraft like the F-16 was so dependent on it.

habu2 wrote:

OK I know this is speculation, but here goes. Somewhere (maybe here) I read/heard that one or more of the TBird jets were towed off to a hangar immediately prior to the start of the show, and then towed back. No proof that the towed jet(s) was actually flown in the show but I'm wondering....

Pre-show, solo pilot goes through all his cockpit checks, including setting baro for MO on the altimeter. Some other problem requires his jet to be towed to the hangar, where it is determined he needs to change to the backup jet. In the hurry and confusion, he jumps in the other jet and taxis back to meet the push for show start. Possible he didn't check/reset baro in the spare jet...

Again, this is pure speculation on my part but it would be a plausible (but not excusable) explanation.

Can anyone comment on the pre-show jet-in&out-of-hangar reports?

#6 was pulled off the line prior to the show start (there were atleast two towed from the line). I have a picture of #6 being towed back into position on the flight line about 1 hour before takeoff. It taxied out for T/O with the rest of the team.

Interesting note that one of the jets (#4 I think) was actually the two seater, it replaced the other jet towed off the line.

Welcome aboard, Jar-breath!

Great to have another active Viper pilot on the forums.

Great explanation of QNH and QFE by one of the janitors - Lieven. Most military fighter types didn't know all that when I was flying. The transport troops who flew all over the world were very familiar with ICAO and all that stuff.

HABU!!!! Gasp. You mean you aren't even IFR rated yet? Sheesh. I vote we take a hat and collect some $$$ for you to have some 'white knuckle' time. Heh heh.

I don't give a rats about what altimiter setting the troop used. If you set the 'window' to zero, then you can fly the whole show with a baro alt referenced to field elevation whether the radar altimiter is working or not. As STBY says, 'tis true, setting the Kollsman window in the Viper affects the HUD readout and other stuff.

I watched the cockpit video a few times and it sure seemed to me that the guy rolled and pulled very soon after the pull-up. I had seen this maneuver many times, and the timing just seemed off to this old phart. Also seemed that he more smash when starting the pull-up. Original demo had the beast pulling up to about 45 degrees at 160 knots or so and simply 'powering' up to the altitude for the roll. This maneuver looked like he was going 200 knots plus. Maybe the video speed is fast on my machine.

In short, people screw up. Most of the time when you screw up in a jet, your widow gets a flag. This one turned out better for the pilot, but left a black eye on the 'birds and fighter jocks in general. We don't need that kinda public relations. Very shady war story on the solo who dies at Hill in early 80's when they were still in the T-38. we can talk about that one later, OK? I was there with my boys, but they didn't see the impact due to the crowd being higher than their little heads.

Finally, I do not believe there was any maintenance factor whatsoever. I also salute KM-eject for all the good poop. I always felt like I had a fighting chance in that seat and was damned glad I never had to try it, heh heh.

out,

Gums wrote:

HABU!!!! Gasp. You mean you aren't even IFR rated yet? Sheesh. I vote we take a hat and collect some $$$ for you to have some 'white knuckle' time. Heh heh.

*SMACK*<---once again, the sound of Gums hitting the nail on the head. My knowledge and procedures are fine, I'm not a total n00b when it comes to flying IFR, in fact I could probably do it without any problems right now. But I just need the money to finish up the 12 stinking hours the FAA says I have to have to get my IFR ticket. The cost of flying has always been high, but now it's even worse.

Hey, even if they are block 25s they're still newer than what we have!!!! Mr. Green

just wanted to re-ask the ?question? posed by Gums. Is there a way to 'zero' out the altimeter to the actual runway 'altitude'? When I flew with a flight team in college, we used to do precision landing events and we always 'zeroed' out our altimeters so we knew exactly how much altitude we had left without having to think too much. Smile

(always my preference!)

also I found this group through another group post about the crash. Today was the first day I heard about it. I am glad everyone walked away from this.

Alan Warfield

You can easily zero out the altimeter. Just spin the knob until the altimeter says 'zero'. You also don't need QNH from ATIS or ground, you can just set field elevation and call it good. If you really want to lawyer it, your MODE-C transmits based on what you tell it, so it's nice to be legal and use what the field is calling, even though it is usually +/- a few feet.

I never used the term QNH until I got to my current base, and the controllers here use ICAO. (Most of you who read my posts can figure out where I am). I never knew what it meant either.

As far as the INS being more accurate than altimeter setting, that's not really true. In the days that Gums flew this jet, until very recently, the INS was a huge pig and would precess like crazy. I don't remember the exact values, but if your system was still within a mile at landing, that was tight. Nowadays, we have ring-laser gyros which measure red-shift of laser light among three axes (for you enginner geeks out there). It's much more precise than the old INUs. Also, we now have GPS that you can slave the INU to via a Kalman filter to zero out bad INU data. I've never seen my INS off by more than about 200 feet. Altitude, or the Z-axis, is still not as easy to tighten down as lat/long. The best way to enhance a position is to show relative motion against it, and if you compare a 300 mile flight across the earth to an altitude delta of +/- 4NM during the whole time of flight, it's hard to get an exact hack. In the viper, you can call up system altitude, but it's largely driven by GPS. I'd still rather use QNH than system elevation any day of the week (unless it comes to using BARO over FCR ranging for weapons delivery.)

Found floating around in cyberspace... yes this is #6 post mortem

habu2, haven't surfed to that site yet... Tburned1 shows the seat in front of the wingtip I see...

Kevin
The Ejection Site

Wow your eyes are better than mine! Looks like both main wheels and possibly one of the hstab/speedbrake assemblies too. looks like the jet struck tail-first then rotated down hard, slamming the nose into the ground and breaking it off. I remember seeing the radome flying out of the fireball in on picture. Extensive fire damage to the right side, more than the left. Wind direction?

Also noticed the Vtail has been wrapped to hide the fact it was a Tbird during transit...

Forum: General

T-Bird crash accident report released