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Tire Limit Speed

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Kyle,

 

Talking about DA and the B737 I got to thinking about tire limit speed.  With DAs above 9,000 feet in the summer the 800 and 900 could get very close to the maximum tire limit speed on T/O from some place such as DEN.  Is this something that PMDG models? With a Vref near 160, the ground speed could be very close to 190.

 

Not sure how it could be modeled and if it really matters, just for conversation.  :smile:

 

blaustern 

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I've not seen a speed limit for the tires in the FCOM Limitations section, I presume that this will vary with tire manufacturer and model.  PMDG has included nose tire balance as a failure item, but I'm not sure a blown tire can be simulated in either FSX or P3D.

 

The landing speeds may seem high, but the acid test for the tires is the rejected takeoff at maximum takeoff weight.  They usually pop the pressure safety plugs and melt down.  PMDG has modeled as much of this as practical given platform limitations.

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Dan,

 

If you look at GS just prior to lift off (Vref), you will see the aircraft groundspeed on the runway.  For the B737NG the tire limit speed is 195.  This was just for conversation and trivia purposes.  :smile:  It would be something that real world NG pilots would know especially those flying in high and hot places.   :smile:

 

blaustern

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Would be a nice feature but in most cases Tire placard speed/limit is only a factor at high airports and abnormal landing configurations. The perfect scenario would be departing SLLP( EL ALTO) at a heavy weight, have to return for and issue and have a flap/slat malfunction when ready for landing. Now you have a higher approach speed due to abnormal configuration. You would have to check your limit speed. Alot of times, tire placard speeds are in miles per hour. You would have to convert it to knots and compare it to approach speeds converted to ground. At high pressure altitude airports, your ground speed increases significantly due to the TAS required to achieve indicated airspeed. Max braking speed can be an issue also in these conditions.

 

The only time i've seen tire speed become a factor was at long runways in the DC10. The DC10 has a variable flap configuration allowing any flap from 5 to 25(5.5, 6.7, 10.2,etc). This allowed you to fully optimize performance and max weights for a given runway. The thing is that long runways result in low flap settings. This is good for performance because it uses the longer runway for acceleration which results in lower flaps/drag at lift off. The lower flap setting requires higher rotate speeds at high gross weights. I've had rotate speeds of 190kts. The plane rolls another 1000ft before it lifts off passing 10 degrees on rotation. The ground speed was 204kts on our 10-30s. On hot thin air days, you would exceed tire limiting weight for conditions. You would have to run a procedure using tire limiting weight to get a higher flap setting to lift off earlier at current weight. Performance work in that jet was fun!!!!  But in most aircraft, it's usual abnormal landing configurations that lead you to trouble.  

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One of my coffee drinking buddies is a B737NG captain.  The other day coming out of DEN in a heavy B739 his ground speed was 190 when he rotated.  Like I say it's just for conversation. :smile:

 

blaustern

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One of my coffee drinking buddies is a B737NG captain.  The other day coming out of DEN in a heavy B739 his ground speed was 190 when he rotated.  Like I say it's just for conversation. :smile:

 

blaustern

And didn't have a tire speed issue. If he had to perform an emergency return along with a abnormal flap landing, there would have been some issues.

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Have you tried a rejected take-off at auw at Kuwait? The day time temperature is around 48c. in reality you would want to be on the ground there for as short a time as possible as you "will" have hot starts!

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Have you tried a rejected take-off at auw at Kuwait? The day time temperature is around 48c. in reality you would want to be on the ground there for as short a time as possible as you "will" have hot starts!

I've spent so much time operating in that region. Summers are brutal and it changes the mindset when applying hot operations procedures. Engine starts require max starter motoring of the engine before introducing fuel. We would go through INS units due to over heat failures. There were times during the day that you couldn't takeoff or land because you exceeded the max certified temperature of 50C. It was not uncommon to have system overheat lights and had to pull covers and open panels to facilitate airflow. Most times you needed a ground AC cart to push cool air into electronic bays. We've had rejects there and pretty much you were done for the day due to brake cooling times let along fuse plugs melting. It was so miserable, you couldn't run the APU until 5 minutes before start because it would overheat after 30 minutes of operation. You would have to spool the engines slowly before setting power. If you poured on the coals too quickly, fuel dumped into the core and spiked the EGT/overheat before the big fan could spin up and generate cooling flow through the engine. After all the hard work getting to the runway, last thing you wanted to do was over temp and return to parking to have the engine scoped. Guys would get dizzy from the heat inside the jet when it's first opened. You would sweat and be soaked to your undies during preflight. You would feel nasty and swampy until 2 hours into flight once it actually cooled off, and then you would freeze for the next few hours from being soaked. Oops, i'm on the soap box lol. I prefer cold weather ops vs hot weather ops lol.

 

From an airline perspective, you are pretty much taken care of. When pushing cargo to the four corners of the world, you're on your own against the elements.

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I spent many years in the Middle East and SE Asia. And I remember one flight back from the Gulf was delayed 6 hours because it was too hot!

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I spent many years in the Middle East and SE Asia. And I remember one flight back from the Gulf was delayed 6 hours because it was too hot!

Yes Sir! The funniest thing is when you transit these areas with new guys. On occasion I make it to Africa, Asia and the MId East during the hottest part of the year. We are sitting in a Gulfstream with Red floor hot messages, amber FWD Floor hot messages, WiFi over heated, and SAT phone/TV systems refuse to turn on. Newbie sitting in the seat with a very concerned look on his/her face. I then grab my headset and ask "ready to get clearance?" lol. They then ask, what about all these warnings, the rectifiers are over heating. I state, it's ok, lets get clearance, lol. I then say "they don't pay for these luxury jets for creature comforts, it's the point A to B they are looking for". That really raises their eyebrows. Once the client shows up, half of the lights extinguish once engines are started. By the time you suck up the gear, all lights are off and all systems are green. These type operations lead to some very good discussions on operational judgment, risk management and hot weather operations/systems.

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Yes Sir! The funniest thing is when you transit these areas with new guys. On occasion I make it to Africa, Asia and the MId East during the hottest part of the year. We are sitting in a Gulfstream with Red floor hot messages, amber FWD Floor hot messages, WiFi over heated, and SAT phone/TV systems refuse to turn on. Newbie sitting in the seat with a very concerned look on his/her face. I then grab my headset and ask "ready to get clearance?" lol. They then ask, what about all these warnings, the rectifiers are over heating. I state, it's ok, lets get clearance, lol. I then say "they don't pay for these luxury jets for creature comforts, it's the point A to B they are looking for". That really raises their eyebrows. Once the client shows up, half of the lights extinguish once engines are started. By the time you suck up the gear, all lights are off and all systems are green. These type operations lead to some very good discussions on operational judgment, risk management and hot weather operations/systems.

Lol you got away with that then! The Middle East is the worst for turbulence as well. flying over the Gulf in August is scary even for crew. Once over the Bosforus we hit clear air turbulence in a 10. The wings bent right up and we dropped like a stone about a thousand feet before recovering. Had that been a 707 the wings would have come off for sure!

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