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00:01
Behind the Prop Intro
Clear prop S73 Cherokee number two following Flint traffic three mile final one trolley bravo makesford in Runway two five going four mile.
00:10
Nick Alan
This is behind the prop with United Flight Systems owner and licensed pilot Bobby Doss and his co host, major airline captain and designated pilot examiner Wally Mulhern. Now let's go behind the prop.
00:24
Bobby Doss
What's up Wally?
00:25
Wally Mulhern
Hey Bobby, how are you?
00:27
Bobby Doss
I am fantastic as always. This is man, summertime in Houston and it is hot. I haven't flown in a small airplane in the last few days. But three digits in the temperature at about 90% humidity does not make for an enjoyable cockpit, I'm sure. So thanks to all the flight instructors and congratulations all the student pilots that are flying fighting through it out there. Today is going to be a show, really a potpourri of things. We've had some questions come in from listeners and just a couple of hot topics that Wally's seen on checkrides and I've seen around the flight school. So we're gonna jump right into it. We're really gonna cover four or five things today. Go arounds. Someone asked some questions about sumping fuel.
01:14
Bobby Doss
We're gonna talk about this hot weather and flying in hot weather and then we're gonna bounce around a little bit with density, altitude and pressure altitude to hopefully make everybody a little bit safer and better pilots this summer time of year. So Wally, let's talk about go arounds, something that I know we've discussed offline quite a bit. Something that I wish I heard more on the radio at our home airport. David Wayne Hooks Lots of traffic, lots going on, lots of changes in the pattern, lots of probably unstabilized approaches being forced down on the ground. You're a pro pilot. What's some of your thoughts as a professional pilot and bigger iron as it relates to going around?
02:00
Wally Mulhern
Well, I know at my airline we have three gates and we call them stabilized approach gates. 1500ft, 1000ft and 500ft. Obviously that's AGL and we have procedures if we're not within a certain window of parameters with airspeed on centerline, configuration of the airplane, landing checklist complete, that sort of things. It is at certain gates it's a mandatory go around. What we try to teach at the airline and really we ought to be doing this in the general aviation world is every approach, every landing should be the same. Whether it's a short Runway, whether it's a long Runway, we should be landing the airplane the same. Because if, you know, we're used to landing on a 10,000 foot Runway every day.
03:00
Wally Mulhern
And then all of a sudden one day we go in and we land on a 7,000 foot Runway or maybe general aviation, maybe a 3,000 foot Runway. We ought to still be doing things the same way. You know, in life we probably do things the same way. You know, you, you wash your hands the same way regardless of what sink you're washing your hands in. I mean, it's a pretty oversimplification of things. But, you know, let's get to where we fly the airplane the same way. I know if I'm landing on a 16,000 foot Runway, I've got a huge margin for error. I can land 5,000ft down the Runway and still have 11,000ft. I can, I can stop the airplane safely within the confines of the concrete. But that's not what we want to do.
03:57
Wally Mulhern
We want to get in the mindset of, boy, I've missed the touchdown zone. I'm going around, I'm going to come back, I'm going to regroup, I'm going to do it again. I remember when I was learning to fly, talking to my father, who was a retired airline pilot, and he told me, he was telling me about his first. And this goes way back. This would have been in the 1950s. His first, what he called it, a root check with Eastern Airlines. The guy giving him the route check, the first thing he asked him about was what was the missed approach procedure at their destination airport. And my father was kind of perplexed that they haven't even gotten off the ground and the guy's asking him missed approach procedures at their destination airport. And the airport they were going to was in mountainous terrain.
04:55
Wally Mulhern
So there were, you know, it wasn't your typical fly, Runway, heading, climb and maintain 2,000ft. There were some, you couldn't do that because of mountains. So I've, that's been with me my entire career is maybe the most important thing about, of course we're talking about instrument approaches is the get out of there procedure. What is my escape procedure? You know, when you get in a movie theater, there's exit signs and there's probably a little briefing before the movie in case of an emergency. Here's, here's how you get out. You get on a commercial airliner and that's what they tell you, here's how you get out. I mean, we haven't even close the door. Or maybe we have closed the door, we haven't even left the gate yet. And they're Telling us how to get out.
05:49
Wally Mulhern
You go on a Coast Guard vessel, the first thing they're doing is telling you know, what the emergency procedures are, the get out procedures. And I think we need to apply that to general aviation and probably be more trigger happy, if you will, on going around. Go arounds are not costly. They cost another 10th of an hour on the hops.
06:17
Bobby Doss
Yes. It's nothing in the grand scheme of things and the consequences are always going to be so much more expensive. You made a comment and I know you didn't necessarily mean it the way I'm going to describe it, but I want the listeners to hear this, maybe some of the student pilots out there listening. But you said if you miss the touchdown zone, you should go around. It's not just that. It's all those other stage gates you talked about. And then it's everything else before that as well. You know, the, a recent conversation I, with someone was the crosswinds were really bad. And I said, well, how far were you from the airport when you realize that? He said like five miles. I'm like, well, why did you try to land? Like, did you have to be there? Was there an emergency? Was there.
07:02
Bobby Doss
Was Wally claiming he was having a heart attack in your plane? Like, you don't have to go there, go. Maybe that's not considered a go around, but go by it. Like, don't even try to land there. And if it's, if you're 1,000ft starting to descend and you forgot the flaps and you realize you're going 90 knots in a Cessna 172, you shouldn't try to get the flaps out. Reconfigure everything. When you're at the 500 foot point right after you overshoot final. I mean, just go around. There's many reasons why you should go around. Not just because you missed your landing target or your spot you were hoping to hit. It's one of those things. I just wish I heard more on the radio, you know. Tower, we're going around. Tower, we're going around.
07:50
Bobby Doss
It would not be the worst thing in the world to hear that all day on the radios.
07:55
Wally Mulhern
Yeah, one thing that my airline added, I don't know, maybe five, seven years ago is we now have a required call out at 500ft. Depending on the approach, we either get an automatic call out at 500ft or the monitoring pilot calls 500ft. But the flying pilot, the person who's going to land the airplane is required to make a stable call at 500ft. So I hear 500. I am as the flying pilot supposed to say stable. And it really makes you think, am I stable? And if you're not and we have definitions of what a stable approach is, I won't get into all that. But if we're not, it is, it's a required go around.
08:49
Bobby Doss
Yep. And it, you're not going to get in trouble, I assume. No one's getting trouble in the world. Absolutely. It's something you actually should practice because if the tower asks for it last minute, you better be ready to do it.
09:03
Wally Mulhern
Yeah, yeah.
09:04
Bobby Doss
Might be things that you're not in your control. So don't be afraid to go around today. If you are going out to practice or flying with an instructor, it's a good thing to have ready to go in your tools, toolkit, something, fuel. This happens every day, thousands of times a day at Hooks Airport. But I do the questions that were asked are like, what are we really looking for? I thought the person asking was asking some good questions. But it's something that you kind of take for granted. You use a fuel cup, you sump some fuel. And I've got some tips that I was given and we'll talk through it a little bit. The, the one thing that I like to do is I like to use a bigger cup.
09:49
Bobby Doss
I think the little itty bitty cups are probably fine, but only if you fill them up right. So you got to get a good chunk of fuel in there. An eighth of an inch of fuel sump is not probably the right thing. And I, so I like to use the bigger cup and then put the gas back in the aircraft if there is no contaminants or water in it. But you're looking for water first. I think in our world, this is Houston, Texas. We've had a lot of big storms, the last few. And planes that are outside that get, you know, an inch of rain dumped on them in a matter of 30 minutes, they either have to have perfect fuel caps or there's going to be a little water in that fuel. Right.
10:31
Bobby Doss
And you really should check that fuel sump, that fuel every time someone puts more fuel or what you think is fuel in those tanks or anytime that you've been away from that plane, it's been out of your control and you're going to go fly that plane, especially if it rained. And a little bit of water is not the end of the world. That's why we're sumping it and if you sump it out, a trick would be to kind of wiggle the wings and rotate the plane a little bit back and forth, you know, shaking the plane, trying to get some of that condensation out and sump it at all of its low points, which is where the sumps are.
11:07
Bobby Doss
I think I see people missing sumps and I go grab them, and maybe they're flying this other end model for the first time, or maybe they're going from N and P models to an S model and there's a whole lot more sumps than there were before. It's important that you get all of those sumps. And we have 20 aircraft. You know, we've had a couple of fuel leaks in our history around sumps. That's going to leave a kind of a pasty blue look on that sump. That's not. That's the dye in the fuel. But that definitely should be looked at by a mechanic and be repaired for sure. But if you don't see light blue in that cup, there's probably a much bigger problem. I've never seen something other than light blue. Wally, have you ever sunked a.
11:59
Bobby Doss
A GA aircraft that used AV gas and had something other than light blue in it?
12:05
Wally Mulhern
I haven't. Other than water. I have seen water in it. But I'll tell you two quick war stories. I was. I was very young, and I was flying with my father. This would have been about 1970. So about 53 years ago, we're in a twin bonanza, and were somewhere in upstate New York, and were getting fuel, and the guy came over and he fueled us. And. And I remember my dad standing outside with the sump. And after he fueled us, my dad started something. And the lineman, the guy who fueled us, looked at me and he said, you know why he's doing that? And, you know, I was 8 years old, 7 years old, and, you know, I didn't know what to say. I said, no. And he said, he says it's because he doesn't trust me. And it. For.
13:05
Wally Mulhern
For a brief period of time, it was really awkward. I'm thinking, oh, you know, you seem like a nice guy. My. My dad shouldn't trust you. Why does he not trust you? And he let me sit there for about 20 seconds. It seemed like about 10 minutes, but it's probably about 20 seconds. And then he said, and he shouldn't trust me. And I. That. That stuck with me for well over 50 years. And, you know, then as were flying home, my dad was explaining to me about fuel and water being heavier, if there's water in the fuel that it would show up. And it was kind of a, you know, a learning moment for a 7 year old or however old I was.
13:53
Wally Mulhern
But I think One thing that CFIs can do to students is, you know, everybody's walking around with a water bottle with them at some point when they sump the, you know, and you got this, you know, two out, maybe two ounces of blue fluid in the cup. Take, take your water bottle and put a couple ounces, put an ounce of water in there and let them see what it actually looks like.
14:25
Bobby Doss
You know, I, I remember somebody doing that for me and it looks a little bit like water and oil. You know, they don't mix for sure.
14:31
Wally Mulhern
Yes, I do. I do remember working at a flight school where they had a water bottle and they had some fuel and water in it in one of the classrooms. And I just remember they had some youth group there or something promoting aviation. And one of the young people there actually drank the, the Avgas. So if you do something like that, I would be very. Tape up that top so it doesn't come off and label it. Do not drink because it, he spit it out real quick.
15:11
Bobby Doss
Nasty. Yeah, so just be careful. Check your fluid. I like to hold it up against the Cessna white color of the paint to make sure it's light blue, doesn't have contaminants. And then if there, you have any questions at all, I obviously ask a flight instructor or the operations or maintenance team at the flight school or the FBO that you're at, so.
15:36
Wally Mulhern
Well, let's stay on fuel for a second because I'll just tell another story. I was, my first aviation job was working as a lineman at an fbo. And you know, I got minim. Minimal training. This is how you do it. Okay, you're good to go. Well, we, the FBO actually opened at 6am but most people didn't get there till 8 in the morning. The lineman got there at 6 in the morning and opened up. And for the first two hours you were usually there solo. And I opened up one day and I knew that were expecting a load of jet fuel. And so I'm there and about 7:15 in the morning, this fuel truck shows up and the driver, I mean he pulls onto the ramp over to where the fuel is.
16:35
Wally Mulhern
And I walk out there and I just said to the driver, I said, do you have a load of jet fuel for us? And he says, yes I do. And I go, great, here it is. I showed him where to offload his jet fuel to us. Well, about 20 minutes later my boss shows up and he goes, what's he doing? I said, we got, it's jet fuel. And he goes, that's not our jet fuel company. That's our avgas company. Mmm, I mean the, you know, the trucks don't say jet a 100 low lead or anything. It's just a tanker truck. So he runs out there and sure enough, this guy is putting 100 low lead into our jet fuel tank.
17:29
Bobby Doss
So.
17:31
Wally Mulhern
You know, they fixed it. But all that fuel had to be taken out of there, had to be refined and separated and everything. And the, you know, the transportation company took care of it. And, but that was a learning lesson. You know, the driver of the truck, jet fuel, AV gas, it's all the same to them. And of course again this was, this is 40 years ago. Hopefully the education is a little bit better. So you know, I was a little bit at fault My, my boss maybe for not I hadn't really been trained very well. But yeah, that could have been an issue.
18:12
Bobby Doss
Well, I, I've heard this, I've never seen it or been a part of it. But you know, the, that accident in planes occurs sometimes with twin engines where they fill up, you know, turbo prop that used jet fuel all day and then they see a big twin that maybe uses AV gas and they try to put the jet fuel in it. That's where I think in ga world we're most susceptible to that happening at the aircraft. But check your fuel, sump your fuel, make sure that you see what you're expecting to see and ask for help when you don't.
18:45
Wally Mulhern
Yeah, and I, I think we do have a, a nomenclature issue in general aviation airplanes. Turbine, turbo, I mean we say turbo prop. A king Air is a turbo prop. Well, my Saratoga is a turbo engine. It's a turbocharged engine, but it's a reset. We burn AV gas, King Air burns jet fuel. So it's, and I hear that with young pilots. Confusion. Turbine, turbo, two different things.
19:20
Bobby Doss
Yeah, that's a big difference for sure. Let's talk about hot weather. It's, it's blazing hot. The humidity is bad here in Houston lately. We're going to see record highs they say in the next few weeks. Cessnas, props, four cylinder engines, they don't produce as much power on these hot days. Let's talk a little Bit about, you know, the things that people should be thinking about as it relates to flying in hot days. I, I think that the performance charts are where we need to see what we need to see. But what do you think about on a hot day in ga not forget your big planes for right now? Do you make any adjustments to your performance thought process? Wally, what do you, what can a pro like you share with some of the listeners is on a hot day?
20:15
Wally Mulhern
Yeah, absolutely. It's, you know, the airplane likes cold weather. Everything about, to an extent, I mean, we can get extreme and that's not good, but a little bit like your, your body, I mean, it's, it's hot and it's damp. In Houston, we had some significant storms roll through the other night. I was without power for almost 48 hours. So, so two nights sleeping in a really hot house and you just wake up, you don't feel rested. You know, airplanes are a lot like people. We don't, we don't like the hot, humid, and we don't perform that well. I mean, I felt kind of lethargic for a couple days. I got air conditioning back on, so all is good now. But airplanes are the same way. And you know, when you density altitude is, I mean, we try to preach this.
21:22
Wally Mulhern
We try to preach this. But, you know, basically here in Houston, we're sort of sea level. Okay, let's just call it sea level or maybe 100, 2, 300ft somewhere in that range. But just to make the math nice and easy, let's call it sea level. We know the higher we go, the performance of the airplane degrades, you know, so maybe from the ground up to 1,000ft, maybe we're climbing it, call it, you know, 700ft per minute, from 7,000 to 8,000ft, we're probably climbing at 200ft per minute. And so then when you look at the density altitude, that's basically where the airplane thinks it is. So here in Houston on. Any idea what is the density altitude today here in Houston? Bobby, any idea?
22:20
Bobby Doss
2097Ft.
22:22
Wally Mulhern
Okay, 2100ft. So we're on the ground. The airplane thinks it's at 2100ft. So something less than 600ft per minute and you know, something Maybe greater than 200ft per minute is going to be our climb performance today. You know, so if you, a hot, humid day, you go load all your friends in the airplane and now we're heavy and you know, make, could be A bad situation.
22:56
Bobby Doss
Yeah. And it's, it is that thought process about, you know, when was the last time me, I'll use me, I'll be the. The guinea pig was last time I really practiced a sure field takeoff. It's probably the week before my commercial check ride. I mean I probably haven't gone out. I fly at an airport. All my planes are an airport that has a 7,000 foot Runway. The small Runway is 3,500ft. I'm not really thinking about trying to get off the ground and go. But if I happen to go somewhere, I would have to really be Johnny on the spot as it related to my performance charts because I don't know that I spend a lot of time in them on a regular basis trying to understand how many feet do I need to really get off the ground.
23:45
Bobby Doss
But I'm just pulled up a quick performance chart. At 2,000ft, the ground roll increases by. At 2,000ft, increases by 40ft. So that's 10%, right. I've heard that it's just less than 10%, but I've heard that term a lot. Right. 10% for every thousand feet of density altitude. That's a pretty good, I guess, rule of thumb. But man, we talk, we use the Denver example a lot I think because it's easy. We all know it's the mile high city and we. You probably use something similar on check rides, Wally. But you know, Denver's Denver is kind of the extreme. But what if my plane was full of people and it was 5,000ft density altitude at Houston, in Houston, that's. That's Denver as far as the planes concerned. Right. And I don't think we would look at those numbers and recognize that.
24:44
Bobby Doss
I did a little work before we got on the air here and San Diego's 235ft, they are at sea level right there. It's like the airport almost touches the sea. Right. So still a couple hundred feet off. And then another airport that most of us could maybe relate to is Napa. Napa's density altitude right now is negative 145ft. Cool dry air in Napa makes for a place where a plane really wants to go fly. And those are three pretty big number spreads from a performance chart perspective. You would need to know what's going on. And so what is.
25:28
Bobby Doss
I don't think I understood density altitude and pressure altitude for a long time in my aviation career because I think it's one of those things that you study and you kind of skip over maybe you don't skip over it, but you, maybe you learn an acronym. High to low, look out below, kind of, some of that stuff, and you probably can work your way through a checkride. But I think as I've been around it a lot longer, right. I think more about how well the props gonna perform, right? How well the engine's gon perform. What's the rule of thumb for leaning the engine? Everyone knows that's at 3,000ft, right? Or the POH probably says it 3,000ft. Well, what if the engine, what if the density altitude is 3,000ft?
26:12
Wally Mulhern
Yeah.
26:13
Bobby Doss
Is the engine gonna perform as well? Right. There's an air fuel mixture, Right. Is the engine even gonna fire as well? Is the prop gonna have enough air to pull the plane through the air and then are the wings going to work as well? All those things are questionable as the air gets less dense.
26:34
Wally Mulhern
Right.
26:34
Bobby Doss
And dense would be thick to me, I think I started making sense when I started thinking that, you know, the air was more like water. Right. Big news story about this submarine. And the water pressure in the bottom of the ocean, right. That's really the same thing that's happening in the air. The closer to sea level, the more weight of the air molecules are creating more pressure. More pressure is more air for the wings to create lift and the prop to move air behind it as well. Right. So hot, humid day, less air molecules, more water in the air, creates less mass for the wings and prop to work. So I would highly recommend that you challenge yourself on a hot day to pretend that you're going to Denver. Even at your home airport. It's not in Denver, but. Yeah.
27:29
Bobby Doss
Pull out the performance charts, understand the distances. It could be catastrophic if you think that you only need a thousand feet, but you really need 1500ft. And while that doesn't sound very realistic, that could be what happens here in Houston, Texas, in the blink of an eye. And that could sneak up and bite you pretty quick.
27:54
Wally Mulhern
Yeah, let's just. You mentioned the different types of altitudes. Density altitude and pressure altitude. I, you know, I'm a pretty simple guy, and high to low, look out below. I'm, I honestly, I'm not quite sure what that means. Okay. But here's what I do know. Pressure altitude. Pressure altitude. And I'm gonna, I'm just gonna make this as simple as. And I, I know how to make it. Pressure altitude is what your altimeter reads when you set it to 2992. That is pressure altitude. So let's say, for instance, we're sitting in an airplane, and the altimeter is 3 triple 0 3,000, and it's indicating field elevation. Okay? And let's make the math simple. Let's say we're at an airport that has a field Elevate is 100ft MSL. So we're sitting in the airplane, we have our altimeter set to 3,000, and it's indicating 100ft.
29:06
Wally Mulhern
Well, to determine what pressure altitude, all we have to do is dial down that altimeter to 2992, and it's going to go down 80ft. So our pressure altitude is going to be 20ft or very close to 20ft. So high altimeter pressure altitude is going to be lower, which is good. Low altimeter. Let's say the altimeter was 2980. Well, now we dial it up to 2992, and it's going to add 120ft. Okay? And most of your performance charts in your books, in your PoH's are based on pressure altitude. So we really should be making that altimeter adjustment. And, you know, we have charts where we can make the adjustment, but I think the simplest way is, man, just think about sitting in an airplane. How do we come up with pressure altitude? I asked this on checkride sometime, and my goodness, the formulas.
30:19
Wally Mulhern
I get the square root of the. Your mother's age divided by your, the number of paws on your dog divided by the street number of your house equals pressure altitude. I mean, I, I've gotten some crazy formulas. It's. It's really pretty simple. Just make that altimeter, say 2992, and you're reading pressure altitude.
30:44
Bobby Doss
Well, I got to be honest. I'm looking at Google right now, and the calculation that they're publishing is a big one. But that's if you don't have an altimeter right in front of you, right? So if you're a pilot and you're at a plane or you're at a flight school and you have the Colesman window there, just tune in 2992 and you'll know what the current pressure altitude is because that altimeter is reading the pressure in the air right then in real time. And you can use that number for your performance charts. The other things are going to make the density feel different for sure, right? The, the temperature and other things. But I think the big one is just turn that number to 1992-and-make some performance chart.
31:33
Bobby Doss
Look at those with that number and you'll have a really good idea what your ground roll and you're clearing a 50 foot obstacle is going to be that day. It might surprise you for sure and that may change your decisions on go around. Right. I think if I was on the, if I was at hooks today and the currently the density out to 2,000ft, I'm going to add 20% to my numbers just as a rule of thumb. And if I needed a thousand feet to get over a 50 foot obstacle, I'm going to assume I need 1200ft today. And that means if I'm not really at the like hotel which is just shy of midpoint there on that Runway, I, I'm not going to go. And that's not that hard to do. Right.
32:15
Bobby Doss
Float a little bit while you're doing touch and goes that you could be there really quick. And that would be my determining factor today for coming back up off the ground. A full stop taxi back would not be the end of the world if you knew those performance numbers. It'd be a lot better than clipping those trees at the end of that Runway for sure.
32:37
Wally Mulhern
Absolutely. You know, and something else I'm. Right now I'm in the middle of doing something I love to do and that's teaching. I have two multi engine students and I'm actually teaching them. Won't be doing their checkride, but I'm instructing them. And we haven't flown yet, but we've done a couple of ground sessions on multi engine performance and everything. And, and just a couple nights ago we had a ground school session and were going through all the performance charts and the data and the particular airplane we're in. I said what is our single engine service ceiling? And they both were able to spit out 4,400ft very quickly. And I thought okay, all right, so here we are in Houston, Texans, Texas. 4400ft. Okay, that, that's workable. And, and I looked at him and I said suppose we're taking off from Denver.
33:37
Wally Mulhern
And it was kind of an aha moment because they both looked at each other and kind of went whoa, that's a problem. That's, you know, that's 800ft underground. So, so we need to be very cognizant of these numbers because in a multi engine airplane we lose an engine, we do have options. Single engine airplane, we lose an engine. We don't, we don't really have options.
34:06
Bobby Doss
Yeah, we just explained Houston today And I know there's the twins flying today. And they're gonna, they're gonna experience if they do the single, if they pull, they stop an engine and they're flying at 4,000ft, they're gonna slowly lose altitude until they get to about 2,000ft today.
34:23
Wally Mulhern
Right.
34:24
Bobby Doss
Because the service ceiling being 4,400 and the 10 to the altitude being just over 2,000.
34:30
Wally Mulhern
Right.
34:30
Bobby Doss
They're not going to be able to stay at 4400 and. Right. That brings into, that brings in towers, buildings, lots of problems even in Houston, Texas.
34:38
Wally Mulhern
Right.
34:39
Bobby Doss
On a day like today. So great example for all those listening out there, for sure. Well, it's been kind of a potpourri of stuff. Hopefully you enjoyed it. Hopefully you learned something. As always, fly safely and stay behind the prop.
34:56
Nick Alan
Thanks for checking out the behind the Prop podcast. Be sure to click subscribe and check us out online@brave.theprop.com behind the prop is recorded in Houston, Texas. Creator and host is Bobby Dawes. Co host is Wally Mulhern. The show is for entertainment purposes only and is not meant to replace actual flight instruction. Thanks for listening and remember, fly safe.